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Document and Entity Information	12 Months Ended
Document and Entity Information	Dec. 31, 2017 shares
Document Information [Line Items]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	SIMO
Entity Registrant Name	SILICON MOTION TECHNOLOGY CORP
Entity Central Index Key	0001329394
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding	143,162,340

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 359,453	$ 274,483
Short-term investments	6,941	3,302
Notes and accounts receivable, net	79,135	73,599
Inventories	94,186	71,887
Restricted assets-current	19,515	44,393
Noncurrent assets held for sale		3,363
Prepaid expenses and other current assets	9,567	5,873
Total current assets	568,797	476,900
Long-term investments		120
Property and equipment, net	51,370	47,892
Deferred income tax assets, net	3,402	3,983
Goodwill	58,964	68,656
Intangible assets, net	7,429	5,227
Other assets	3,770	3,248
Total assets	693,732	606,026
Current Liabilities
Notes and accounts payable	56,423	31,739
Bank loan	25,000	25,000
Income tax payable	11,492	20,271
Current portion of long-term payable	566	240
Accrued expenses and other current liabilities	83,763	68,736
Total current liabilities	177,244	145,986
Long-term payable, net of current portion	108	367
Other long-term liabilities	22,329	16,910
Total liabilities	199,681	163,263
Commitments and Contingencies (Note 18)
Shareholders' Equity
Ordinary Shares at US$0.01 par value per share Authorized: 500,000 thousand shares Issued and outstanding: 141,311 thousand shares in 2016 and 143,162 thousand shares in 2017	1,431	1,413
Additional paid-in capital	242,487	226,658
Accumulated other comprehensive income (loss)	2,643	(1,032)
Retained Earnings	247,490	215,724
Total shareholders' equity	494,051	442,763
Total liabilities and shareholders' equity	$ 693,732	$ 606,026

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Ordinary Shares, par value	$ 0.01	$ 0.01
Ordinary Shares, Authorized	500,000,000	500,000,000
Ordinary Shares, Issued	143,162,000	141,311,000
Ordinary Shares, outstanding	143,162,000	141,311,000

Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
NET SALES	$ 523,404	$ 556,146	$ 361,297
COST OF SALES	272,210	281,541	176,765
GROSS PROFIT	251,194	274,605	184,532
OPERATING EXPENSES
Research and development	102,053	92,405	71,161
Sales and marketing	25,868	25,765	20,173
General and administrative	16,933	17,072	15,714
Impairment of goodwill	10,337	0	0
Amortization of intangible assets	2,534	2,103	1,051
Gain from disposal of noncurrent assets held for sale	(1,880)
Total operating expenses	155,845	137,345	108,099
OPERATING INCOME	95,349	137,260	76,433
NON-OPERATING INCOME (EXPENSES)
Gain from disposal of short-term investments	103	2	3
Interest income	4,268	2,158	2,025
Foreign exchange gain (loss), net	(157)	(692)	76
Impairment of long-term investments	(120)	(13)
Interest expense	(423)	(127)	(47)
Other income (loss), net	(19)	42	10
Total non-operating income	3,652	1,370	2,067
INCOME BEFORE INCOME TAX	99,001	138,630	78,500
INCOME TAX EXPENSE	24,046	27,690	18,249
NET INCOME	$ 74,955	$ 110,940	$ 60,251
EARNINGS PER ORDINARY SHARE:
Basic	$ 0.53	$ 0.79	$ 0.44
Diluted	$ 0.52	$ 0.78	$ 0.43
WEIGHTED AVERAGE ORDINARY SHARES OUTSTANDING
Basic (Thousands)	142,738	140,919	138,100
Diluted (Thousands)	143,606	142,050	139,634
EARNINGS PER ADS (one ADS equals four ordinary shares):
Basic	$ 2.10	$ 3.15	$ 1.75
Diluted	$ 2.09	$ 3.12	$ 1.73
WEIGHTED AVERAGE ADS OUTSTANDING
Basic (Thousands)	35,684	35,230	34,525
Diluted (Thousands)	35,902	35,513	34,909

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 74,955	$ 110,940	$ 60,251
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX EFFECT OF NIL
Change in net foreign currency translation adjustments	3,390	(1,555)	(1,868)
Change in deferred pension gain (loss)	285	(110)	(4)
OTHER COMPREHENSIVE INCOME (LOSS)	3,675	(1,665)	(1,872)
TOTAL COMPREHENSIVE INCOME	$ 78,630	$ 109,275	$ 58,379

Consolidated Statements Of Changes In Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (accumulated deficit)
Beginning Balance at Dec. 31, 2014	$ 304,100	$ 1,356	$ 190,783	$ 2,505	$ 109,456
Beginning Balance, shares at Dec. 31, 2014		135,622
Net income	60,251				60,251
Other comprehensive income	(1,872)			(1,872)
Issuance of ordinary shares for Shannon Systems acquisition	7,640	$ 16	7,624
Issuance of ordinary shares for Shannon Systems acquisition, Shares		1,560
Stock-based compensation expenses	10,418		10,418
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units, shares		2,339
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units	441	$ 23	418
Dividends declared	(36,480)				(36,480)
Ending Balance at Dec. 31, 2015	344,498	$ 1,395	209,243	633	133,227
Ending Balance, shares at Dec. 31, 2015		139,521
Net income	110,940				110,940
Other comprehensive income	(1,665)			(1,665)
Stock-based compensation expenses	17,364		17,364
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units, shares		1,790
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units	69	$ 18	51
Dividends declared	(28,443)				(28,443)
Ending Balance at Dec. 31, 2016	$ 442,763	$ 1,413	226,658	(1,032)	215,724
Ending Balance, shares at Dec. 31, 2016	141,311	141,311
Net income	$ 74,955				74,955
Other comprehensive income	3,675			3,675
Stock-based compensation expenses	15,494		15,494
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units, shares		1,851
Issuance of ordinary shares upon exercise of employee stock options and restricted stock units	353	$ 18	335
Dividends declared	(43,189)				(43,189)
Ending Balance at Dec. 31, 2017	$ 494,051	$ 1,431	$ 242,487	$ 2,643	$ 247,490
Ending Balance, shares at Dec. 31, 2017	143,162	143,162

Consolidated Statements Of Changes In Shareholders' Equity (Parenthetical) - $ / shares			3 Months Ended								12 Months Ended
	Oct. 24, 2017	Oct. 24, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends declared, per share	$ 0.3	$ 0.2	$ 0.075	$ 0.050	$ 0.050	$ 0.050	$ 0.0500	$ 0.0375	$ 0.0375	$ 0.0375	$ 0.30	$ 0.20	$ 0.2625

Consolidated Statements Of Cash Flows - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

CASH FLOWS FROM OPERATING ACTIVITIES

Net income

$ 74,955

$ 110,940

$ 60,251

Adjustments to reconcile net income to net cash provided by operating activities:

Depreciation and amortization

10,599

9,482

7,936

Amortization of intangible assets

2,534

2,103

1,051

Gain from disposal of short-term investments

(103)

(2)

(3)

Impairment of long-term investments

120

Stock-based compensation

15,494

17,364

10,418

Loss on disposal of property and equipment

Impairment of goodwill

10,337

Gain from disposal of noncurrent assets held for sale

(1,880)

Deferred income taxes

581

(3,373)

911

Changes in operating assets and liabilities:

Short-term investments

(3,208)

(2,710)

Notes and accounts receivable

(5,156)

(14,620)

(29,179)

Inventories

(22,299)

(24,777)

(410)

Prepaid expenses and other current assets

1,585

(1,313)

(664)

Other assets

(138)

(5)

136

Notes and accounts payable

24,248

9,198

7,651

Accrued expenses and other current liabilities

458

12,180

11,020

Income tax payable

(8,779)

6,876

(4,301)

Other liabilities

4,529

4,179

1,119

Net cash provided by operating activities

103,881

125,568

65,946

CASH FLOWS FROM INVESTING ACTIVITIES

Purchase of held-to-maturity financial assets

(4,000)

Proceeds from sale of held-to-maturity financial assets

4,000

Business acquisition-net of cash, cash equivalents, and restricted cash acquired

(2,865)

(30,286)

Increase of prepaid expenses and other current assets

(508)

Purchase of property and equipment

(11,683)

(12,220)

(23,664)

Net cash used in investing activities

(14,548)

(8,220)

(58,458)

CASH FLOWS FROM FINANCING ACTIVITIES

Proceeds from issuance of ordinary shares upon exercise of employee stock options

380

494

Proceeds from bank loan

25,000

Repayments of bank loan

(25,000)

Dividends paid

(32,120)

(22,899)

(20,765)

Net cash provided by (used in) financing activities

(31,740)

2,194

(20,271)

NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH

57,593

119,542

(12,783)

^[1]

EFFECT OF EXCHANGE RATE CHANGES

2,753

(521)

(953)

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF YEAR

321,177

202,156

^[1]

215,892

^[1]

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, END OF YEAR

381,523

321,177

202,156

^[1]

SUPPLEMENTAL INFORMATION

Interest paid

367

105

Income taxes paid

30,910

$ 24,300

20,494

Cash paid for business acquisition, net of cash, cash equivalents, and restricted cash acquired

2,865

30,286

Shannon Systems

CASH FLOWS FROM INVESTING ACTIVITIES

Business acquisition-net of cash, cash equivalents, and restricted cash acquired

(30,286)

SUPPLEMENTAL INFORMATION

Fair value of assets acquired, net of cash, cash equivalents, and restricted cash acquired

43,661

Issuance of stock

(7,640)

Cash paid for business acquisition, net of cash, cash equivalents, and restricted cash acquired

30,286

Shannon Systems | Other Noncurrent Liabilities

SUPPLEMENTAL INFORMATION

Other liabilities

$ (5,735)

Bigtera

CASH FLOWS FROM INVESTING ACTIVITIES

Business acquisition-net of cash, cash equivalents, and restricted cash acquired

(2,865)

SUPPLEMENTAL INFORMATION

Fair value of assets acquired, net of cash, cash equivalents, and restricted cash acquired

4,586

Cash paid for business acquisition, net of cash, cash equivalents, and restricted cash acquired

2,865

Bigtera | Other Noncurrent Liabilities

SUPPLEMENTAL INFORMATION

Other liabilities

(477)

Bigtera | Other Current Liabilities

SUPPLEMENTAL INFORMATION

Other liabilities

$ (1,244)

[1]	The restricted cash is only included in the amount of "as adjusted" item.

Organization and Operations

12 Months Ended

Dec. 31, 2017

Organization and Operations

1. ORGANIZATION AND OPERATIONS

Silicon Motion Technology Corporation (“SMTC”, collectively with its subsidiaries the “Company”) is the global leader in supplying NAND flash controllers for solid state storage devices and the merchant leader in supplying SSD controllers. The Company has the broadest portfolio of controller technologies and solutions and ship over 750 million NAND controllers annually, more than any other company in the world. The Company’s controllers are widely used in embedded storage products such as SSDs and eMMCs which are found in smartphones, PCs and industrial and commercial applications. The Company also supply specialized high-performance hyperscale datacenter and industrial SSD solutions. The Company’s customers include most of the NAND flash vendors, storage device module makers and leading OEMs.

The Company acquired SMI Taiwan in April 2005. Originally SMI Taiwan was known as Feiya Technology Corporation (“Feiya”), a Taiwan corporation which was incorporated in April 1997 but had changed its name to SMI Taiwan after acquiring in August 2002 Silicon Motion, Inc., a California corporation (“SMI USA”), which was incorporated in November 1995. Feiya was originally a flash memory products company and SMI USA a graphics processor company. In April 2007, the Company acquired FCI, a leading designer of RF ICs for mobile TV and wireless communications based in South Korea. In July 2015, the Company acquired Shanghai Baocun Information Technology Co., Ltd. (“Shannon Systems”), China’s leading enterprise-class PCIe SSD company based in Shanghai, China. In July 2017, the Company acquired Bigtera, a software defined storage company.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP). The consolidated financial statements include the accounts of SMTC and its wholly-owned subsidiaries. The Company owns 100% of the outstanding shares in all of its subsidiaries. All significant intercompany balances and transactions have been eliminated upon consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect certain reported amounts and disclosures. The actual results could differ from those estimates.

Concentration of Credit Risk and Significant Customers

Financial instruments that potentially subject the Company to a significant concentration of credit risk consist principally of cash equivalents, short term investments and accounts receivable. Cash, cash equivalents and short-term investments balances are maintained with high quality financial institutions, the composition and maturities of which are regularly monitored by management. The Company believes that the concentration of credit risk in its trade receivables, is substantially mitigated by the Company’s credit evaluation process, relatively short collection terms and the high level of credit worthiness of its customers. The Company performs ongoing credit evaluations of its customers’ financial conditions and limits the amount of credit extended based upon payment history and the customer’s current credit worthiness. The Company regularly reviews the allowance for bad debt and doubtful accounts by considering factors such as historical experience, credit quality, age of the accounts receivable balances and current economic conditions that may affect a customer’s ability to pay.

Historically, a relatively small number of customers have accounted for a significant portion of our net revenue. Sales to one customer in 2015 and 2016, and two customers in 2017 accounted for 10% or more of the Company’s net sales, and these sales represented 30%, 28% and 39% of the Company’s net sales in 2015, 2016 and 2017, respectively. In 2015 and 2016, the significant customer was SK Hynix and in 2017, SK Hynix and Intel. The Company’s top ten customers in 2015, 2016 and 2017 accounted for approximately 72%, 75% and 72% of net sales, respectively.

Fair Value of Financial Instruments

The carrying amount of the Company’s financial instruments, including cash and cash equivalents, notes and accounts receivable and notes and accounts payables approximates fair value due to the short-term maturity of the instruments. Fair values of short-term investments represent quoted market prices, if available. If no quoted market prices are available, fair values are estimated based on discounted cash flow, or other valuation techniques. Long-term investments in privately-held companies with no readily determinable market value are recorded using the cost method, since the cost of obtaining verifiable fair value is unreasonably high. The Company periodically evaluates these investments for impairment. If it is determined that an other-than-temporary decline has occurred in the carrying value, an impairment loss is recorded for that period. The Company’s long-term liabilities approximate their fair values as they contain interest rates that vary according to market interest rates.

Fair value is the price that would be received upon sale of an asset or paid upon transfer of a liability in an orderly transaction between market participants at the measurement date and in the principal or most advantageous market for that assets or liability. The fair value should be calculated based on assumptions that market participants would use in pricing the asset or liability, not on assumptions specific to the Company. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value. The hierarchy prioritizes the inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of the three levels which is determined by the lowest level input that is significant to the fair value measurement in its entirety. These levels are:

Level 1 — Use unadjusted quoted prices in active markets for identical assets or liabilities.

Level 2 — Use observable inputs other than Level 1 prices such as quoted prices for identical or similar instruments in markets that are not active, quoted prices for similar instruments in active markets, and model-based valuation in which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 — Use inputs that are generally unobservable and reflect the use of significant management judgments and estimates.

See Note 20, “Fair Value Measurement”, for the related disclosure.

Cash Equivalents

The Company considers all highly liquid instruments acquired with a remaining maturity of three months or less when purchased to be cash equivalents. In addition, time deposits with maturities ranging from more than three months to one year are considered qualified as cash equivalents as the nature of the time deposits are similar to cash such that without advance notice to the bank, they can be readily converted into known amounts of cash with the principal of the time deposits protected and not subject to penalty in the event of an early withdrawal. Also, the risk of changes in value because of changes in interest rates is insignificant due to the fact that the Company can still earn interest based on a rate close to the on-going published interest rate applicable for the actual period of the time deposits in the event of an early withdrawal. Cash and cash equivalents are stated at cost, which approximates their fair value.

Short-term Investments

The Company’s short-term investments primarily includes short-term income yielding investments with original maturities greater than three months from the purchase date and remaining maturities less than one year. These short-term investments consist mostly of bond funds and principal protected notes that are bought and held principally for the purpose of selling them in the near term and are classified as trading securities as well as senior notes classified as held-to-maturity investments with maturities less than one year. Trading securities are reported at fair value with the subsequent changes in fair value recorded in earnings as unrealized gains and losses. Senior notes are measured at amortized cost using the effective interest method less any impairment.

Allowance for Doubtful Receivables

An allowance for doubtful receivables is provided based on a review of the collectability of accounts receivables. The Company determines the amount of allowance for doubtful receivables by examining the historical collection experience and current trends in the credit quality of its customers as well as its internal credit policies.

Inventories

Inventories are stated at the lower of cost or market value. Inventories are recorded at standard cost and adjusted to the approximate weighted-average cost at the balance sheet date. Market value represents the current replacement cost for raw materials, work in process and finished goods. The Company assesses its inventory for estimated obsolescence or unmarketable inventory based upon management’s assumptions about future demand and market conditions. In estimating reserves for obsolescence, the Company primarily evaluates estimates based on the timing of the introduction of new products and the quantities remaining of old products and provides reserves for inventory on hand in excess of the estimated demand. Estimated losses on slow-moving items are recognized and included in the allowance for losses.

Long-term Investments

The Company has long-term investments in companies that it does not exercise significant influence and accounts for these investments under the cost method. Management regularly evaluates financial information related to these investments to determine whether an other than temporary decline in their value exists. Factors indicative of an other than temporary decline include recurring operating losses, credit defaults and subsequent rounds of financings at an amount below the cost basis of the investment. Management periodically weighs all quantitative and qualitative factors in determining if any impairment loss exists. When a decline in value is deemed to be other-than-temporary, the Company recognizes an impairment loss in other income and expense.

Noncurrent Assets Held for Sale

Non-current assets are presented separately as held for sale when the Company is committed to selling the asset, an active plan of sale has commenced, and the sale is expected to be completed within 12 months. Assets held for sale are measured at the lower of their carrying amount and fair value less cost to sell. Assets held for sale are no longer amortized or depreciated.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation. Significant additions, renewals and betterments are capitalized, while maintenance and repairs are expensed as incurred.

Depreciation is computed using the straight-line method over estimated useful lives that range as follows: buildings — 25 to 50 years; machinery and equipment — 3 to 6 years; furniture and fixtures — 3 to 8 years; software — 1 to 5 years; leasehold and buildings improvement — the shorter of the estimated useful life or lease term, which is generally 2 to 6 years. Depreciation expense recognized for the years ended December 31, 2015, 2016 and 2017 was approximately US$7,936 thousand, US$9,482 thousand and US$10,599 thousand, respectively.

Upon the sale or other disposal of property and equipment, the related cost and accumulated depreciation are removed from the accounts, and any gain or loss is credited or charged to operating income.

Government Grants

Grants received by the Company from the Korean government to assist with specific research and development activities are deducted from those research and development costs incurred, in the period in which the related expenses are incurred, to the extent that they are non-refundable. Government grants that were used for the acquisition of fixed assets are deducted from the acquisition costs of the acquired assets and amortized over the useful lives of the related assets. The Company recognizes refundable government grants as long-term payable and current portion of long-term payable on its consolidated balance sheet.

Goodwill and Intangible Assets

Goodwill is the excess of the purchase price paid over the fair value of the net tangible and intangible assets acquired in a business combination. Intangible assets, which consist primarily of development technology, are amortized over their estimated useful lives, of 3.5 to 5.5 years.

Impairment of Goodwill and Long-Lived Assets

The Company evaluates the recoverability of long-lived assets whenever events or changes in circumstances indicate the carrying value may not be recoverable. The determination of recoverability is based on an estimate of undiscounted cash flows expected to result from the use of an asset and its eventual disposition. The estimate of cash flows is based upon, among other things, certain assumptions about expected future operating performance, growth rates and other factors. Estimates of undiscounted cash flows may differ from actual cash flows due to, among other things, technological changes, economic conditions, changes to the business model or changes in operating performance. If the sum of the undiscounted cash flows is less than the carrying value, an impairment loss is recognized, measured as the amount by which the carrying value exceeds the fair value of the asset. Fair value is determined by reference to quoted market prices, if available, or discounted cash flows, as appropriate. See Note 11, “Goodwill and Acquired Intangible Assets,” regarding impairment testing in fiscal year 2015, 2016 and 2017.

The Company monitors the recoverability of goodwill recorded in connection with acquisitions, by reporting unit, annually, or sooner if events or changes in circumstances indicate that the carrying amount may not be recoverable. The Company conducts its annual impairment test of goodwill on November 30. Reporting units may be operating segments as a whole or an operation one level below an operating segment, referred to as a component. Prior to fiscal 2017, goodwill impairment is tested using a two-step approach. The first step compares the fair value of a reporting unit to its carrying amount, including goodwill. If the fair value of the reporting unit is greater than its carrying amount, goodwill is not considered impaired and the second step is not required. If the fair value of the reporting unit is less than its carrying amount, the second step of the impairment test measures the amount of the impairment loss, if any, by comparing the implied fair value of goodwill to its carrying amount. If the carrying amount of goodwill exceeds its implied fair value, an impairment loss is recognized equal to that excess. The implied fair value of goodwill is calculated in the same manner that goodwill is calculated in a business combination, whereby the fair value of the reporting unit is allocated to all of the assets and liabilities of that unit, with the excess purchases price over the amounts assigned to assets and liabilities.

In January 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2017-04, which removes step two from the goodwill impairment test. The Company elected to early adopt this ASU in the fourth quarter of 2017, in conjunction with the Company’s annual review for impairment.

Estimating fair value is performed by utilizing various valuation approaches, such as income approach or market approach. The total of all reporting unit fair values was also compared to the Company’s market capitalization plus control premium for reasonableness. See Note 11, “Goodwill and Acquired Intangible Assets,” regarding impairment testing.

Other Assets

Other assets primarily consist of industrial property right and deposits for office leases.

Restricted Assets

Restricted assets consist of deposits required for litigation and restricted cash. Restricted cash represents cash set aside as collateral for obtaining capacity and borrowings as well as cash received from government grants with restriction on its usage.

Bank loans

Loans from financial institutions are stated at the amount of unpaid principal. Bank loans comprise borrowings which are held by banks based in Taiwan.

Other long-term liabilities

Other long-term liabilities primarily consist of payable to former shareholders of Shannon Systems and unrecognized tax benefit.

Pension Costs

Revenue Recognition

Revenue from product sales is generally recognized upon shipment to the customer provided that the Company has received a signed purchase order, the price is fixed or determinable, transfer of title has occurred in accordance with the shipping terms specified in the arrangement with the customer, collectibility from the customer is considered reasonably assured, product returns are reasonably estimable and there are no remaining significant obligations or customer acceptance requirements. Revenue on development service orders is generally recognized upon completion and customer acceptance of contractually agreed milestones.

The Company grants certain distributors limited rights of return and price protection rights on unsold products. The return rights are generally limited to five percent of the monetary value of products purchased within the preceding six months, provided that the distributor places a corresponding restocking order of equal or greater value. An allowance for sales returns for distributors and all customers is recorded at the time of sale based on historical returns information available, management’s judgment and any known factors at the time the financial statements are prepared that would significantly affect the allowance. Price protection rights are based on the inventory products the distributors have on hand at the date the price protection is offered. A reserve for price adjustments is recorded based on the estimated products on hand at the distributors and historical experience. The actual price adjustments to distributors incurred by the Company are minimal.

The Company provides a warranty period of one year for manufacturing defects of its products. Warranty returns have been infrequent and relate to defective or off-specification parts. The Company estimates a reserve for warranty based on historical experience and records this amount to cost of sales. For the years ended December 31, 2015, 2016 and 2017, the Company did not experience significant costs associated with warranty returns.

Research and Development

Research and development costs consist of expenditures incurred during the course of planned research and investigation aimed at the discovery of new knowledge that will be useful in developing new products or at significantly enhancing existing products as well as expenditures incurred for the design and testing of product alternatives. All expenditures related to research and development activities of the Company are charged to operating expenses when incurred. Third-party research and development costs are expensed when the contracted work has been performed or as milestone results have been achieved.

Income Taxes

The provision for income tax represents income tax paid and payable for the current year plus changes in the deferred income tax assets and liabilities during the years. Deferred income tax assets are recognized for net operating loss carryforwards, research and development credits, and temporary differences. The Company believes that uncertainty exists regarding the realizability of certain deferred income tax assets and, accordingly, has established a valuation allowance for those deferred income tax assets to the extent the realizability is not deemed to be more likely than not. Deferred income tax assets and liabilities are measured using enacted tax rates.

The Company utilizes a two step approach to recognizing and measuring uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained in a dispute with taxing authorities, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount which is more than 50% likely of being realized upon ultimate settlement. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. The Company records interest and penalties related to unrecognized tax benefits in income tax expense.

Foreign Currency Transactions

Foreign currency transactions are recorded at the rates of exchange in effect when the transaction occurs. Gains or losses, resulting from the application of different foreign exchange rates when cash in foreign currency is converted into the entities’ functional currency, or when foreign currency receivables and payables are settled, are credited or charged to income in the period of conversion or settlement. At the balance sheet date, assets and liabilities denominated in foreign currencies are remeasured based on prevailing exchange rates and any resulting gains or losses are credited or charged to income.

Translation of Foreign Currency Financial Statements

The reporting currency of the Company is the U.S. dollars. The functional currency of some of the Company’s subsidiaries is the local currency of the respective entity. Accordingly, the financial statements of the foreign subsidiaries were translated into U.S. dollars at the following exchange rates: assets and liabilities — current rate on the balance sheet date; shareholders’ equity — historical rates; income and expenses — average rate during the period. The resulting translation adjustment is recorded as a separate component of comprehensive income.

Comprehensive Income (Loss)

Comprehensive income and loss represents net income (loss) plus the results of certain changes in shareholders’ equity during a period from non-owner sources. The following table presents the components of accumulated other comprehensive income (loss) as of December 31, 2015, 2016 and 2017:


	Year Ended December 31, 2015									Year Ended December 31, 2016									Year Ended December 31, 2017
	US$									US$									US$
	Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)
Beginning balance		3,354			(849	)		2,505			1,486			(853	)		633			(69	)		(963	)		(1,032	)
Current-period change		(1,868	)		(4	)		(1,872	)		(1,555	)		(110	)		(1,665	)		3,390			285			3,675

Ending balance		1,486			(853	)		633			(69	)		(963	)		(1,032	)		3,321			(678	)		2,643

Legal Contingencies

The Company is regularly involved in various claims and legal proceedings. Periodically, the Company reviews the status of each significant matter and assesses the potential financial exposure. If the potential loss from any claim or legal proceeding is considered probable and the amount can be estimated, the Company accrues a liability for the estimated loss. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, the Company reassesses the potential liability related to the pending claims and litigation and revises these estimates as appropriate. Such revisions in the estimates of the potential liabilities could have a material impact on the results of operations and financial position.

Earnings Per Share

Basic earnings per share are computed by dividing net earnings attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. Diluted earnings per share reflect the potential dilution that could occur if stock options and other dilutive securities were exercised. Dilutive securities are excluded from the computation of the diluted income per share in periods when their effect is anti-dilutive. The Company’s dilutive securities consist of employee stock options and restricted stock units. The effect of dilutive securities including employee stock options and restricted stock units were 1,534 thousand shares (384 thousand ADSs), 1,131 thousand shares (283 thousand ADSs) and 868 thousand shares (218 thousand ADSs) for the years ended December 31, 2015, 2016 and 2017, respectively.

Stock-Based Compensation

The Company accounts for stock-based compensation in accordance with ASC 718 Compensation — Stock Compensation. The Company uses the Black-Scholes valuation model for the valuation of stock options and recognizes compensation expense on a straight-line basis over the requisite service period of the award. The value of our restricted stock units is based on the fair value of our shares on the date of grant and expensed over the vesting period.

Prior to the initial declaration of a quarterly cash dividend on January 22, 2013, the fair value of restricted stock units (“RSUs”) was measured based on the grant date share price, as the Company did not historically pay cash dividends on our common stock. For awards granted on or subsequent to January 22, 2013, the fair value of RSUs was measured based on the grant date share price, less the present value of expected dividends during the vesting period, discounted at a risk-free interest rate.

Dividends

Our Board of Directors declared payment of our first quarterly dividend on our common stock in January 2013 and the first dividend payment was made on March 4, 2013. Our Board of Directors has subsequently declared and paid dividends in each successive quarter. On October 24, 2016 and October 24, 2017, our Board of Directors, instead of declaring a quarterly dividend, declared an annual dividend payable in four quarterly installments. The payment of future cash dividends are subject to the Board’s continuing determination that the payment of dividends are in the best interests of the Company’s shareholders and are in compliance with all laws and agreements of the Company applicable to the declaration and payment of cash dividends.

Recent Accounting Pronouncements

In May 2014, the FASB issued a new standard related to revenue recognition. Under the new standard, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In addition, the new standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. In August 2015, the FASB issued an amendment to defer the effective date. The new standard is effective for fiscal years beginning after December 15, 2017 and early adoption is permitted for annual reporting periods beginning after December 15, 2016. In March and April 2016, the FASB issued two accounting updates to clarify the implementation guidance on principal versus agent considerations, performance obligations and the licensing. In addition, the FASB issued another accounting update in May 2016 to address narrow-scope improvements to the guidance on collectability, noncash consideration, and completed contracts at transition and provides a practical expedient for contract modifications at transition. The new guidance is required to be applied retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying it recognized at the date of initial application. The Company will adopt this new standard as of January 1, 2018, using the modified retrospective method with the cumulative effect of initially applying it recognized at the date of initial application. The Company has finalized its assessment and has identified that the adoption of this new standard will not have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In April 2015, the FASB issued an accounting update regarding the measurement date of a defined benefit obligation and plan assets. The amendment permits the entity with a fiscal year-end that does not coincide with a month-end to measure defined benefit plan assets and obligations using the month-end that is closest to the entity’s fiscal year-end. If a contribution or significant event (such as a plan amendment, settlement, or curtailment that calls for a remeasurement in accordance with existing requirements) occurs between the month-end date used to measure defined benefit plan assets and obligations and an entity’s fiscal year-end, the entity should adjust the measurement of defined benefit plan assets and obligations to reflect the effects of those contributions or significant events. This amendment is effective for fiscal years beginning after December 15, 2016 and early application is permitted. The adoption of this amendment did not have a material impact on the Company’s results of operations, financial position or cash flow.

In July 2015, the FASB issued an accounting update to simplify the measurement of inventory. The amendment requires the measurement of inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendment applies to inventories for which cost is determined by methods other than the last-in first-out and the retail inventory methods. This amendment is effective prospectively for annual periods beginning after December 15, 2016 and early application is permitted. The adoption of this amendment did not have a material impact on the Company’s results of operations, financial position or cash flow.

In November 2015, the FASB issued an accounting update to simplify the presentation of deferred income taxes. The amendment requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. The current requirement that deferred tax liabilities and assets of a tax-paying component of an entity be offset and presented as a single amount is not affected by the amendments in this guidance. This amendment is effective prospectively or retrospectively for annual periods beginning after December 15, 2016 and early application is permitted. The Company elected to have an early adoption of the amendment as of December 31, 2015, and the adoption of this amendment did not have a material impact on the Company’s financial position.

In February 2016, the FASB issued a new standard regarding leases (Topic 842). The new standard requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases other than that the entity elects the short-term lease recognition and measurement exemption. Qualitative and quantitative disclosures will be enhanced to better understand the amount, timing and uncertainty of cash flows arising from leases. In January 2018, the FASB issued an amendment that permits an entity to elect an optional transition practical expedient to not evaluate under Topic 842 land easements that exist or expired before the entity’s adoption of Topic 842 and that were not previously accounted for as leases under Topic 840, the current standard regarding leases. The guidance is effective for fiscal years beginning after December 15, 2018, and early adoption is permitted. The Company is currently evaluating the effect this standard will have on its financial position, results of operations, cash flow and financial statement disclosures.

In March 2016, the FASB issued an accounting update to simplify several aspects of the accounting for share-based payment award transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendment is effective for fiscal years beginning after December 15, 2016, and earlier adoption is permitted. The adoption of this amendment did not have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In June 2016, the FASB issued an accounting update to amend the guidance on the impairment of financial instruments that are not measured at fair value through profit and loss. The amendment introduces a current expected credit loss (CECL) model based on expected losses rather than incurred losses to estimate credit losses on financial instruments measured at amortized cost and requires a broader range of reasonable and supportable information to estimate expected credit loss. In addition, under the amendment, an entity recognizes an allowance for expected credit losses on financial instruments measured at amortized cost and available-for-sale debt securities rather than the current methodology of delaying recognition of credit losses until it is probable a loss has been incurred. The amendment is effective for fiscal years beginning after December 15, 2019, and earlier adoption is permitted as of the fiscal years beginning after December 15, 2018. The adoption of the amendments is not expected to have a material impact on the Company’s statement of cash flows.

In August 2016, the FASB issued an accounting update to clarify the following eight cash flow classification issues: (1) debt prepayment or debt extinguishment costs, (2) settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, (3) contingent consideration payments made after the acquisition date of a business combination, (4) proceeds received from the settlement of insurance claims, (5) proceeds received from the settlement of corporate-owned life insurance policies, including bank-owned life insurance policies, (6) distributions received from equity method investees, (7) beneficial interests in securitization transactions, and (8) separately identifiable cash flows and application of the predominance principle. The amendment is an improvement to reduce the current and potential future diversity in practice. The amendment is effective for fiscal years beginning after December 15, 2017, and earlier adoption is permitted. In addition, the amendment should be applied using a retrospective transition method to each period presented. The Company is currently evaluating the impact that the adoption will have on its statement of cash flows.

In October 2016, the FASB issued an accounting update to simplify the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. The amendment removes the prohibition against the recognition of current and deferred income tax effects of intra-entity transfers of assets other than inventory until the asset has been sold to an outside party. The amendment is effective for fiscal years beginning after December 15, 2017, and earlier adoption is permitted. The adoption of this amendment is not expected to have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In October 2016, the FASB issued an accounting update to amend the consolidation guidance on how a reporting entity that is the single decision maker of a variable interest entity (“VIE”) should treat indirect interests in the entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of that VIE. Under this amendment, the single decision maker is required to consider that indirect economic interests in the VIE held through related parties that are under common control on a proportionate basis. However, this amendment does not change the existing characteristics of a primary beneficiary. The amendment is effective for fiscal years beginning after December 15, 2016, and earlier adoption is permitted. The adoption of this amendment did not have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In November 2016, the FASB issued an accounting update related to the classification and presentation of changes in restricted cash on the statement of cash flows. The amendment requires restricted cash or restricted cash equivalents should be included with cash and cash equivalent when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The amendment is effective for fiscal years beginning after December 15, 2017, and early adoption is permitted. The Company has elected to adopt the amendment as of December 31, 2016, and the retrospective transition approach is applied to prior reporting periods presented. The adoption of this amendment did not have a material impact on the Company’s financial position.

The following table reflects the adjustments made to the consolidated statements of cash flows to confirm prior period classifications under the new guidance for the periods presented:


	As Reported			Adjustment			As Adjusted
	US$			US$			US$
Year Ended December 31, 2014:
Net cash provided by operating activities		68,725			—			68,725
Net cash provided by (used in) investing activities		(15,413	)		3,817			(11,596	)
Net cash used in financing activities		(19,710	)		—			(19,710	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		33,602			3,817			37,419
Effect of exchange rate changes		(1,111	)		—			(1,111	)
Cash, cash equivalents, and restricted cash* at beginning of year		161,720			17,864			179,584

Cash, cash equivalents, and restricted cash* at end of year		194,211			21,681			215,892

Year Ended December 31, 2015:
Net cash provided by operating activities		65,946			—			65,946
Net cash used in investing activities		(58,414	)		(44	)		(58,458	)
Net cash used in financing activities		(20,271	)		—			(20,271	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		(12,739	)		(44	)		(12,783	)
Effect of exchange rate changes		(953	)		—			(953	)
Cash, cash equivalents, and restricted cash* at beginning of year		194,211			21,681			215,892

Cash, cash equivalents, and restricted cash* at end of year		180,519			21,637			202,156

*	The restricted cash is only included in the amount of “as adjusted” item.

To early adopt the accounting update, the Company has amended the presentation of changes in cash and cash equivalents by explaining the changes in the total of cash, cash equivalents, and restricted cash. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the statement of cash flows.


	As of December 31
	2014		2015		2016		2017
	US$		US$		US$		US$
Cash and cash equivalents		194,211		180,519		274,483		359,453
Restricted cash included in restricted assets-current		19,322		19,328		44,393		19,515
Restricted cash included in other assets		2,359		2,309		2,301		2,555

Total cash, cash equivalents, and restricted cash shown in the statements of cash flows		215,892		202,156		321,177		381,523

Amounts included in restricted cash represent (a) cash and time deposits set aside as collateral for obtaining capacity; (b) cash received from government grants with restriction on its usage; and (c) cash and time deposits that are pledged for short-term loans.

In January 2017, the FASB issued an accounting update to clarify the definition of a business to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendment provides a screen to determine when an integrated set of assets and activities (collectively referred to as a “set”) is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. If the screen is not met, the amendment requires that to be considered a business, a set must include an input and a substantive process that together significantly contribute to the ability to create output. The amendment is effective for fiscal years beginning after December 15, 2017. The Company is currently evaluating the impact that the adoption will have on its results of operations, financial position, cash flow and disclosures.

In January 2017, the FASB issued an accounting update to simplify the accounting treatment for the impairment of goodwill. The amendment eliminates Step 2 from the goodwill impairment test, which measures a goodwill impairment loss by calculating the implied fair value of goodwill by assigning the fair value of a reporting unit to all of its assets and liabilities as if that reporting unit had been acquired in a business combination. Instead, under this amendment, the entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value and the impairment loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. The amendment is effective for fiscal years beginning after December 15, 2019, and early adoption is permitted. The Company adopted this amendment beginning in fiscal 2017 and performed the annual goodwill impairment test in accordance with the amended guidance. Refer to Note 11 for discussion of the annual goodwill impairment test.

In February 2017, the FASB issued an accounting update to clarify the scope of asset derecognition guidance and accounting for partial sales of nonfinancial assets. The amendment defines the term “in substance nonfinancial asset” as a financial asset promised to counterparty in a contract if substantially all of the fair value of assets (recognized and unrecognized) that are promised to the counterparty in the contract is concentrated in nonfinancial assets and clarifies that an entity should identify each distinct nonfinancial asset or in substance nonfinancial asset promised to a counterparty and derecognize each asset when a counterparty obtains control of it. The amendment also clarifies that an entity should allocate consideration to each distinct asset by applying the guidance in Topic 606 on allocating the transaction price to performance obligations. Under this amendment, an entity is required to derecognize a distinct nonfinancial asset or distinct in substance nonfinancial asset in a partial sale transaction when it (1) does not have (or ceases to have) a controlling financial interest in the legal entity that holds the asset in accordance with Topic 810 and (2) transfers control of the asset in accordance with Topic 606. Once an entity transfers control of a distinct nonfinancial asset or distinct in substance nonfinancial asset, it is required to measure any noncontrolling interest it receives (or retains) at fair value. The amendment is effective for fiscal years beginning after December 15, 2017 and early adoption is permitted. The amendment should be applied on a full or modified retrospective basis. The adoption of this amendment is not expected to have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In March 2017, the FASB issued an accounting update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The amendment requires that an entity disaggregates the service cost component from the other components of net benefit cost and present the service cost component with other current compensation costs for related employees in the income statement. The amendment also requires an entity presents the other components elsewhere in the income statement and outside of income from operation if such subtotal is presented and allow only the service cost component of net benefit cost to be eligible for capitalization. The amendment is effective for fiscal years beginning after December 15, 2017 and early adoption is permitted. The amendment should be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively, on and after the effective date, for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. The amendment allows for a practical expedient that permits an entity to use the amounts disclosed in its pension and other postretirement benefit plan note for the prior comparative periods as the estimation basis for applying the retrospective presentation requirements. The Company intends not to apply the practical expedient for apply the retrospective presentation requirements. The adoption of this amendment is not expected to have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

In May 2017, the FASB issued an accounting update to provide clarity and reduce both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, Compensation—Stock Compensation, to a change in the terms or conditions of a share-based payment award. Under the amendment, modification accounting is required to be applied unless all of the following are the same immediately before and after the change: (1) the award’s fair value (or calculated value or intrinsic value, if those measurement methods are used); (2) the award’s vesting conditions; and (3) the award’s classification as an equity or liability instrument. The amendment is effective for fiscal years beginning after December 15, 2017 and early adoption is permitted. The amendment should be applied prospectively to an award modified on or after the adoption date. The adoption of this amendment is not expected to have a material impact on the Company’s financial position, results of operations, cash flow and financial statement disclosures.

Business Acquisition

12 Months Ended

Dec. 31, 2017

Business Acquisition

3. BUSINESS ACQUISITION

Shannon

On July 1, 2015, the Company completed its acquisition of Shannon Systems, China’s leading enterprise-class PCIe SSD company based in Shanghai, China. In exchange for 100% of the outstanding shares of common stock of Shannon Systems, the Company issued 1,560 thousand ordinary shares with fair value of US$7,640 thousand and paid approximately US$37,925 thousand in cash. The value of the 1,560 thousand ordinary shares issued was determined based on the market value of the Company’s common shares at the date of the acquisition, discounted for the fact that the shares are restricted as to their marketability for a period of five years from the issuance date. In 2015, the Company incurred US$359 thousand of acquisition costs which comprised primarily of transaction fees and direct acquisition costs, including legal, accounting, and other professional fees. These costs are included in the line item of “operating expenses—general and administrative” on the consolidated statements of income.

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition:


	US$
Cash, cash equivalents and restricted cash		1,904
Accounts receivable, net		946
Inventories		2,624
Other current assets		288
Property and equipment		71
Goodwill		33,204
Identifiable intangible assets		8,381
Accounts payable		(644	)
Accrued expenses and other current liabilities		(1,209	)

Net assets acquired		45,565

As of December 31, 2017, approximately US$5,735 thousand has not been paid to the former shareholders of Shannon Systems and is included in other long-term liabilities on the consolidated balance sheets as of both December 31, 2016 and 2017.

The excess of the purchase price over the fair value of the net tangible assets acquired has been reflected as identifiable intangible assets. The identifiable intangible assets and respective useful lives are as follows:


	US$		Useful Life
Developed technology		3,789		3.5
In-process research and development (“IPR&D”)		4,592		indefinite

Total identifiable intangible assets		8,381

Developed technology represented the existing know-how in enterprise-class PCIe SSD including all the developed and in-process products for the Shannon Systems business.

The estimated fair value of IPR&D was defined as research and development projects related to enterprise-class PCIe SSDs in-process at the time of the transaction that had not demonstrated their technological feasibility and that do not have an alternative future use.

Goodwill represents the excess of the purchase price over the estimated fair values of the net tangible and intangible assets. The factors that contributed to the recognition of goodwill primarily relate to expansion into new product areas and potential synergies created from combined capabilities, and goodwill is not expected to be deductible for tax purposes.

The results of Shannon Systems since the acquisition date included on the consolidated statement of income for the year ended December 31, 2015 were as follows:


	US$
Net sales		9,049
Net income		421

The operating results of Shannon Systems have been included in the Company’s operations beginning July 1, 2015. The following unaudited pro forma information represents a summary of the results of operations as if the acquisition occurred on January 1, 2014 and 2015 and includes certain pro forma adjustments, including amortization of identifiable intangibles from that date (in thousands except earnings per share):


	Year Ended December 31
	2014		2015
Net sales		293,562		364,670
Net income		42,483		58,468
Earnings per share
Basic		0.31		0.42
Diluted		0.31		0.42
Weighted average ordinary shares outstanding (thousand)
Basic		136,164		138,880
Diluted		138,347		140,414

The pro forma results are based on various assumptions and are not necessarily indicative of what would have occurred had the acquisition closed on January 1, 2014 and 2015.

Bigtera

On July 3, 2017, the Company completed its acquisition of Bigtera, a software defined storage company. In exchange for 100% of the outstanding shares of common stock of Bigtera, the Company paid approximately US$4,664 thousand in cash. In 2017, the Company incurred US$171 thousand of acquisition costs which comprised primarily of transaction fees and direct acquisition costs, including legal and other professional fees. These costs are included in the line item of “operating expenses—general and administrative” on the consolidated statements of income.

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition:


	US$
Cash, cash equivalents and restricted cash		78
Accounts receivable, net		380
Other current assets		14
Property and equipment		15
Goodwill		625
Identifiable intangible assets		4,736
Accounts payable		(436	)
Accrued expenses and other current liabilities		(748	)

Net assets acquired		4,664

As of December 31, 2017, approximately US$1,721 thousand has not been paid to the former shareholders of Bigtera and is included in other current and long-term liabilities on the consolidated balance sheets as of December 31, 2017.


	US$		Useful Life
Know-how		3,753		5.5
Current technology		983		5.5

Total identifiable intangible assets		4,736

Know-how represents software device storage (SDS) technology that has value through its continued use or reuse across all version of Bigtera’s software products. Such know-how derives independent value from not being generally known and is the subject of efforts that are reasonable under the circumstances to maintain its secrecy.

Current technology represents the part of technology that is unique in current version of software products.

The results of Bigtera since the acquisition date included on the consolidated statement of income for the year ended December 31, 2017 were as follows:


	US$
Net sales		2,993
Net income		(314	)

The operating results of Bigtera have been included in the Company’s operations beginning July 3, 2017. The following unaudited pro forma information represents a summary of the results of operations as if the acquisition occurred on January 1, 2016 and 2017 and includes certain pro forma adjustments, including amortization of identifiable intangibles from that date (in thousands except earnings per share):


	Year Ended December 31
	2016		2017
Net sales		557,672		523,849
Net income		109,736		73,834
Earnings per share
Basic		0.78		0.52
Diluted		0.77		0.51
Weighted average ordinary shares outstanding (thousand)
Basic		140,919		142,738
Diluted		142,050		143,606

The pro forma results are based on various assumptions and are not necessarily indicative of what would have occurred had the acquisition closed on January 1, 2016 and 2017.

Cash, Cash Equivalents, and Restricted Cash

12 Months Ended

Dec. 31, 2017

Cash, Cash Equivalents, and Restricted Cash

4. CASH, CASH EQUIVALENTS, AND RESTRICTED CASH


	December 31
	2016		2017
	US$		US$
Cash and deposits in bank		58,391		59,751
Time deposits		199,064		269,392
Bonds acquired under repurchase agreements		17,028		30,310

Total cash and cash equivalents		274,483		359,453
Restricted cash (Note 2)		46,694		22,070

	321,177		381,523

Short-Term Investments

12 Months Ended

Dec. 31, 2017

Short-Term Investments

5. SHORT-TERM INVESTMENTS


	December 31
	2016		2017
	US$		US$
Trading securities		3,302		6,941

The Company classified certain short-term investments as trading securities. Realized gains on sales of these trading securities were US$3 thousand, US$2 thousand and US$103 thousand for the years ended December 31, 2015, 2016 and 2017, respectively. The amount of unrealized losses related to trading securities at year end was nil for the years ended December 31, 2015, 2016 and 2017, respectively.

Notes and Accounts Receivable

12 Months Ended

Dec. 31, 2017

Notes and Accounts Receivable

6. NOTES AND ACCOUNTS RECEIVABLE


	December 31
	2016			2017
	US$			US$
Trade accounts receivable		75,946			81,165
Allowance for doubtful accounts		(723	)		(598	)
Allowance for sales returns and discounts		(1,624	)		(1,432	)

	73,599			79,135

The changes in the allowances are summarized as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Allowances for doubtful accounts
Balance, beginning of year		1,167			775			723
Reversals charged to expense, net		(392	)		(12	)		(125	)
Write-offs		—			(40	)		—

Balance, end of year		775			723			598


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Allowances for sales returns and discounts
Balance, beginning of year		1,427			1,555			1,624
Additions charged to expense, net		1,753			3,285			3,093
Actual sales return and discount		(1,625	)		(3,216	)		(3,285	)

Balance, end of year		1,555			1,624			1,432

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Inventories

12 Months Ended

Dec. 31, 2017

Inventories

7. INVENTORIES

The components of inventories are as follows:


	December 31
	2016		2017
	US$		US$
Finished goods		24,782		41,365
Work in process		31,185		25,090
Raw materials		15,920		27,731

		71,887		94,186

The Company wrote down US$2,525 thousand, US$2,995 thousand and US$698 thousand in 2015, 2016 and 2017, respectively, for estimated obsolete or unmarketable inventory.

Long-Term Investments

12 Months Ended

Dec. 31, 2017

Long-Term Investments

8. LONG-TERM INVESTMENTS

As of December 31, 2016 and 2017, the Company held equity investments in several privately-held companies with the carrying value as follows:


	Percentage of Ownership						December 31
	2016			2017			2016		2017
							US$		US$
Cost method:
Cashido Corp. (Cashido)		2.1	%		2.1	%		91		—
Vastview Technology, Corp. (Vastview)		2.9	%		2.9	%		29		—

								120		—

In July 2001, the Company invested in the common stock of Cashido. At the time of investment, Cashido manufactured flash memory storage devices. Cashido currently focuses on the manufacture of computer accessories and ozone based sterilization devices. In 2016 and 2017, the Company recognized impairment charges of US$13 thousand and US$91 thousand in its investment in Cashido, respectively.

In December 2006 and February 2007, the Company invested US$3,360 thousand in the common stock of Vastview. Vastview is a fabless semiconductor company that develops and markets driver ICs and other ICs for the TFT-LCD industry. In 2009 and 2013, the Company received US$808 thousand and US$46 thousand from capital reductions at Vastview. From 2008 to 2010, the Company recognized impairment charges of US$2,462 thousand in its investment in Vastview, and an additional charge of US$29 thousand in 2017. The impairment charges were mainly due to the declining financial performances of the investees.

The Company accounts for these investments using the cost method. These investments are evaluated for impairment on an annual basis or as circumstances warrant.

Noncurrent Assets Held for Sale

12 Months Ended

Dec. 31, 2017

Noncurrent Assets Held for Sale

9. NONCURRENT ASSETS HELD FOR SALE


	December 31
	2016		2017
	US$		US$
Assets held for sale		3,363		—

		3,363		—

The Company vacated from an office building located in Shanghai, China and in 2016 took action to sell the property. The sale plan met all of the held-for-sale criteria in accordance with ASC 360—Property, Plant and Equipment and the asset was reclassified accordingly. In 2017, the Company sold the property to a non-affiliated third party and recognized a gain from disposal of US$1,880 thousand.

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property and Equipment

10. PROPERTY AND EQUIPMENT


	December 31
	2016		2017
	US$		US$
Cost:
Land		9,309		9,309
Buildings		29,232		30,288
Machinery and equipment		18,122		21,665
Furniture and fixtures		6,760		7,746
Leasehold and buildings improvement		4,911		5,497
Software		22,745		24,864

Total		91,079		99,369

Accumulated depreciation:
Buildings		2,708		3,472
Machinery and equipment		14,032		15,665
Furniture and fixtures		4,207		5,212
Leasehold and buildings improvement		3,591		4,213
Software		19,130		19,874

		43,668		48,436
Prepayment and construction in progress		481		437

		47,892		51,370

In April 2006, the Company began leasing a property located in Taipei, Taiwan to a third party. The lessee has been renewing the operating lease annually and last renewed in March 2018. Net carrying value of the properties as of December 31, 2016 and 2017 was US$728 thousand and US$709 thousand, respectively. Annual rental income from the lease is about US$42 thousand each year.

Goodwill and Acquired Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Acquired Intangible Assets

11. GOODWILL AND ACQUIRED INTANGIBLE ASSETS

Intangible assets: The intangible assets acquired from the Company’s acquisition of FCI and Centronix in 2007, BTL in 2011, Shannon Systems in 2015 and Bigtera in 2017 are as follows:


	December 31
	2016									2017
	US$									US$
	Cost		Accumulated Impairment		Accumulated Amortization			Net Carrying Amount		Cost		Accumulated Impairment		Accumulated Amortization			Net Carrying Amount
Acquisition-related intangible assets		8,381		—		(3,154	)		5,227		13,117		—		(5,688	)		7,429

No impairment losses were recognized in 2015, 2016 and 2017. Amortization expense of acquisition-related intangible assets for the years ended December 31, 2015, 2016 and 2017 were US$1,051 thousand, US$2,103 thousand and US$2,534 thousand, respectively.

Goodwill: Goodwill is not amortized, but instead is reviewed and tested for impairment at least annually and whenever events or circumstances occur which indicate that goodwill might be impaired. The goodwill that resulted from the Company’s acquisition of FCI and Centronix in 2007 and purchased of BTL’s assets in 2011 was US$66,300 thousand. As a result of the acquisition of Shannon Systems in 2015 and Bigtera in 2017, the Company recorded additional goodwill of US$33,204 thousand and US$625 thousand, respectively. Impairment of goodwill is tested at the Company’s reporting unit level by comparing the carrying amount, including goodwill, to the fair value. In performing the analysis, the Company uses the best information available, including reasonable and supportable assumptions and projections. Goodwill is tested for impairment annually on November 30. Total goodwill was US$68,656 thousand and US$58,964 thousand as of December 31, 2016 and 2017, respectively. The Company recognizes an impairment charge for the amount by which the carrying amount of the reporting unit exceeds its implied fair value. For the year ended December 31, 2017, the Company has elected to adopt ASU 2017-04 (as described in note 2 above). Under the updated guidance, the Company applied a one-step quantitative test and recorded the amount of goodwill impairment as the excess of a reporting unit’s carrying amount over its fair value. Fair value determinations are sensitive to changes in the underlying assumptions and factors including those relating to estimating future operating cash flows to be generated from the reporting unit which are dependent upon historical data and internal forecasts and projections developed by management. The Company’s strategic plans, estimates of perpetual growth rate taking into account the annual goodwill impairment analysis of the current economic environment and the timing and degree of any economic recovery and market participant assumptions. Key assumptions within the five-year discounted cash flow analysis prepared for the annual goodwill impairment analysis included revenue growth rates, projected gross margins, perpetual growth rate and risk-adjusted discount rate that the Company determined to be appropriate. The inputs used are classified as Level 3 within the fair value hierarchy due to the significance of unobservable inputs using company-specific information. As a result of the goodwill impairment test conducted as of November 30, 2017, the Company determined that the carrying amounts for mobile communication unit exceed its fair value and recorded a goodwill impairment charge of US$10,337 thousand in the fourth quarter of 2017. The company used an income approach (discounted cash flow model) to determine the fair value of the mobile communication unit. The impairment charge was mainly attributable to a new project cancellation by a customer and delayed commercialization of a new product.


	December 31
	2016										2017
	US$										US$
	Cost		Accumulated Impairment			Foreign Currency Adjustment			Net Carrying Amount		Cost		Accumulated Impairment			Foreign Currency Adjustment			Net Carrying Amount
Goodwill		99,504		(30,808	)		(40	)		68,656		100,129		(41,145	)		(20	)		58,964

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Short-Term Bank Loans

12 Months Ended

Dec. 31, 2017

Short-Term Bank Loans

12. SHORT-TERM BANK LOANS


	December 31
	2016		2017
	US$		US$
Secured loans		25,000		25,000

	25,000		25,000

The interest expenses for the years ended December 31, 2015, 2016 and 2017 were nil, US$105 and US$387 thousand, respectively.

In 2016 and 2017, the Company obtained US dollar revolver credit facilities from two banks and drew down US$25,000 thousand in 2016 and 2017, respectively. Interest rates ranged from 0.953% to 1.51% per annum on monthly outstanding loans. In 2016, loans were secured by US$25 million of pledged deposits, which were recorded as current restricted cash, and in 2017, loans no longer required pledged deposits. The US$25 million of loans is expected to be repaid in 2018.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2017

Accrued Expenses and Other Current Liabilities

13. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES


	December 31
	2016		2017
	US$		US$
Wages and bonus		29,028		29,629
Dividends		21,382		32,451
Research and development payable		5,456		5,638
License fees and royalties		4,021		3,729
Professional fees		2,038		2,286
Equipment		492		1,844
Others		6,319		8,186

	68,736		83,763

Pension Plan

12 Months Ended

Dec. 31, 2017

Pension Plan

14. PENSION PLAN

SMI Taiwan, the Company’s largest operating company is a Taiwan registered company and subject to Taiwan’s Labor Pension Act (the “Act”), which became effective on July 1, 2005, and the pension mechanism under the Act is deemed a defined contribution plan. The employees who were subject to the Labor Standards Law prior to July 1, 2005 could choose to be subject to the pension mechanism under the Act or continue to be subject to the pension mechanism under the Labor Standards Law. For those employees who were subject to the Labor Standards Law prior to July 1, 2005 and still work for the same company after July 1, 2005 and have chosen to be subject to the pension mechanism under the Act, their seniority as of July 1, 2005 were maintained. The Act prescribes that the rate of contribution by an employer to employees’ pension accounts per month will not be less than 6% of each employee’s monthly salary. According to the Act, SMI Taiwan made monthly contributions and recognized pension costs of US$1,015 thousand, US$1,272 thousand and US$1,579 thousand for the years ended December 31, 2015, 2016 and 2017, respectively.

The Company provides a defined benefit plan to the employees of SMI Taiwan under the Labor Standards Law that offers benefits based on an employee’s length of service and average monthly salary for the six-month period prior to retirement. The Company contributes an amount equal to 2% of salaries paid each month to a pension funds (the “Funds”), which is administered by the Labor Pension Fund Supervisory Committee established by the government (the “Committee”) and deposited in the Committee’s name in the Bank of Taiwan. Before the end of each year, the Company assesses the balance in the Funds. If the amount of the balance in the Funds is inadequate to pay retirement benefit for employees who conform to retirements in the next year, the Company is required to fund the difference in one appropriation that should be made before the end of March of the next year. The government is responsible for the administration of all the defined benefit plans for the companies in Taiwan under the Labor Standards Law. The government also sets investment policies and strategies, determines investment allocation and selects investment managers. As of December 31, 2016 and 2017, the asset allocation was primarily in cash, equity securities and debt securities. Furthermore, under the Labor Standards Law, the rate of return on assets shall not be less than the average interest rate on a two-year time deposit published by the local banks. The government is responsible for any shortfall in the event that the rate of return is less than the required rate of return. However, information on how investment allocation decisions are made, inputs and valuation techniques used to measure the fair value of plan assets, the effect of fair value measurements using significant unobservable inputs on changes in plan assets for the period and significant concentrations of risk within plan assets is not fully made available to the Company by the government. Therefore, the Company is unable to provide the required fair value disclosures related to pension plan assets. Future contributions will be based on 2% of the employee salaries at that time. The Company estimates its contribution for the year ending December 31, 2018 to be US$69 thousand which was determined based on 2% of estimated salaries in 2018.

Starting in 2010, the Company provides a defined benefit pension plan to the Korean employees of FCI with at least one year of service. FCI’s overall investment strategy is to avoid a negative return on plan assets. FCI estimates its contribution for the year ending December 31, 2018 to be nil.

For employees under defined contribution pension plans, pension costs are recorded based on the actual contributions made to employees’ individual pension accounts. For employees under defined benefit pension plans, pension costs are recorded based on actuarial calculations. Determining the cost associated with such benefits is dependent on various actuarial assumptions, including discount rate, expected return on plan assets, compensation increase, employee mortality and turnover rates. The Company reviewed its actuarial assumptions at the measurement date on December 31 every year. The effect of modifications to assumptions is recorded in accumulated other comprehensive loss and amortized to net periodic cost over future periods using the corridor method. The Company believes that assumptions utilized in recording its obligations under its plans are reasonable based on its experience and market conditions. Independent actuaries perform the required calculations to determine expense in accordance with U.S. GAAP. Actual results may differ from the actuarial assumptions and are generally accumulated and amortized into earnings over future periods. The net periodic costs are recognized as employees render services necessary to earn the benefits.

The changes in benefits obligation and plan assets and the reconciliation of funded status are as follows:


	December 31
	2015			2016			2017
	US$			US$			US$
Change in benefit obligation
Projected benefit obligation at beginning of year		3,320			3,632			4,242
Service cost		273			487			1,572
Interest cost		57			104			336
Actuarial loss (gain)		79			151			(665	)
Benefits paid		(97	)		(132	)		(354	)

Projected benefit obligation at end of year		3,632			4,242			5,131

Change in plan assets
Fair value of plan assets at beginning of year		2,556			2,800			3,902
Actual return on plan assets		33			33			81
Employer contributions		328			1,203			1,358
Benefits paid		(117	)		(134	)		(227	)

Fair value of plan assets at end of year		2,800			3,902			5,114

Funded status recognized as an other asset (liabilities)		(832	)		(340	)		(17	)

Amounts recognized in accumulated other comprehensive income consist of the following:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Net loss		852		963		678
Transition obligation		1		—		—

Total recognized in accumulated other comprehensive income		853		963		678

The accumulated benefit obligation for all defined benefit pension plans was US$2,098 thousand, US$2,648 thousand and US$ 3,210 thousand at December 31, 2015, 2016 and 2017, respectively.

The components of net periodic benefit cost are as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Service cost		273			487			1,572
Interest cost		57			104			336
Projected return on plan assets		(47	)		(28	)		(58	)
Amortization of unrecognized net transition obligation and unrecognized net actuarial gain		27			11			37

Net periodic benefit cost		310			574			1,887

Other changes in plan assets and benefit obligation recognized in other comprehensive loss:


	2015		2016			2017
	US$		US$			US$
Recognize the decrease in net gain (loss)		4		111			(285	)
Amortization of net gain (loss)		—		(1	)		—

Total recognized in other comprehensive loss (income)		4		110			(285	)

The estimated net gain for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year is US$33 thousand.

Expected benefit payments:


	US$
2018		188
2019		184
2020		407
2021		181
2022		182
2023 and thereafter		2,057

The actuarial assumptions to determine the benefit obligations were as follows:


	2015						2016						2017
	Taiwan			Korea			Taiwan			Korea			Taiwan			Korea
Weighted-average assumptions used to determine benefit obligations:
Discount rate		1.75	%		3.90	%		1.50	%		3.80	%		1.63	%		4.10	%
Rate of compensation increase		4.25	%		4.00	%		4.25	%		3.50	%		4.25	%		3.50	%
Weighted-average assumptions used to determine net projected benefit cost:
Discount rate		1.75	%		3.90	%		1.50	%		3.80	%		1.63	%		4.10	%
Expected long-term return on plan assets		2.00	%		1.20	%		2.00	%		1.10	%		1.75	%		1.10	%
Rate of compensation increase		4.25	%		4.00	%		4.25	%		3.50	%		4.25	%		3.50	%

In 2016 and 2017, FCI’s pension plan assets were invested in principal guaranteed interest insurance contracts and fixed bank deposits, which are principal and interest guaranteed products and are classified as Level 2. These Level 2 securities were valued by discounting future cash flows using benchmark yield rates.

The fair values of FCI’s pension plan assets at December 31, 2016 and 2017 are as follows:


	December 31
	2016		2017
	US$		US$
Guaranteed interest contract
Kyobo Life Insurance Co. Ltd.		1,284		1,599
Shinhan Investment Co. .		—		374
Fixed deposit
Industrial Bank of Korea		1,537		1,892

		2,821		3,865

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

15. INCOME TAXES

The components of income tax expense are as follows:


	Year Ended December 31
	2015		2016			2017
	US$		US$			US$
Current		17,338		31,063			23,465
Deferred		911		(3,373	)		581

Income tax expense		18,249		27,690			24,046

The income (loss) before income taxes for domestic and foreign entities is as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Domestic		(12,037	)		(20,663	)		(27,902	)
Foreign		90,537			159,293			126,903

		78,500			138,630			99,001

Since the Company is based in the Cayman Islands, a British overseas territory with no corporate income tax, tax on pretax income is calculated at the Cayman Islands statutory rate of zero for each year.

The Company and its subsidiaries file separate income tax returns. A reconciliation of income tax expense on pretax income at statutory rate and income tax expense is shown below:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Tax expense at statutory rate of Cayman		—			—			—
Differences between Cayman and foreign statutory tax rates		18,765			34,415			24,255
Tax-exempt income		(906	)		(4,648	)		—
Permanent differences		(1,065	)		(7,792	)		(4,249	)
Temporary differences		(330	)		(1,533	)		(1,445	)
Alternative minimum tax		4			594			4
Income tax (10%) on undistributed earnings		2,460			5,677			2,709
Net changes in income tax credit		(897	)		(495	)		166
Net changes in valuation allowance of deferred income tax assets		1,621			1,724			(2,401	)
Net operating loss carryforwards		(2,052	)		(1,689	)		1,492
Liabilities related to unrealized tax benefits		672			2,385			3,455
Adjustment of prior years’ taxes and others		(23	)		(948	)		60

Income tax expense		18,249			27,690			24,046

Deferred income tax assets (liabilities) are as follows:


	December 31
	2016			2017
	US$			US$
Notes and accounts receivable		44			44
Stock-based compensation		1,146			771
Allowance for sales return		205			154
Inventory reserve		1,646			1,311
Foreign currency translation		2			( 5	)
Property and equipment		383			168
Investment tax credits		8,647			9,078
Net operating loss carryforwards		12,335			10,391
Others		411			562
Valuation allowance		(20,836	)		(19,072	)

		3,983			3,402

The valuation allowance shown in the table above relates to net operating loss carryforwards, tax credits and temporary differences for which the Company believes that realization is uncertain. Valuation allowance increased by US$2,253 thousand and US$1,792 thousand for the years ended December 31, 2015 and 2016, respectively, and decreased by US$1,764 thousand for the year ended December 31, 2017. The increase in valuation allowance in 2015, and 2016 was primarily due to uncertainty in generating sufficient taxable income in the foreseeable future and utilizing operating loss carryforwards and research and development credits before they expire. The decrease in valuation allowance in 2017 was primarily due to the lower Federal corporate income tax rate that followed the enactment of the Tax Cuts and Jobs Act of 2017.

Starting from 2018, the corporate income tax rate in Taiwan increased from 17% to 20%. In addition, the rate of the corporate surtax applicable to 2018 unappropriated earnings was reduced from 10% to 5%. Deferred tax assets recognized as at December 31, 2017 are expected to be adjusted and would increase by US$529 thousand in 2018.

As of December 31, 2017, FCI had unused research and development tax credits of approximately US$4,546 thousand which will expire in the period from 2018 to 2022.

As of December 31, 2017, the Company’s United States federal net operating loss carryforwards for federal income tax purposes were approximately US$9,760 thousand. If not utilized, the federal net operating loss carryforwards will expire in 2037.

As of December 31, 2017, the Company’s United States federal and state research and development tax credit carryforwards for federal and state income tax purposes were approximately US$2,601 thousand and US$1,785 thousand, respectively. If not utilized, the federal tax credit carryforwards will expire starting in 2037 while the state tax credit carryforward has no expiration date.

Current United States federal and California state laws include substantial restrictions on the utilization of net operating losses and credits in the event of an “ownership change” of a corporation. Accordingly, the Company’s ability to utilize net operating loss and tax credit carryforwards may be limited as a result of such “ownership change”. Such a limitation could result in the expiration of carryforwards before they are utilized.

As of December 31, 2017, the Company had accumulated undistributed earnings from a foreign subsidiary of US$325 million. No deferred tax liability was recorded in respect of those amounts as these earnings are considered indefinitely reinvested. It is not practicable to estimate the amount of unrecognized deferred tax liabilities for these undistributed foreign earnings.

Unrecognized Tax Benefit

A reconciliation of the beginning and ending balances of the total amounts of unrecognized tax benefits is as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Balance, beginning of year		4,655			5,639			10,286
Increases in tax positions taken in current year		2,337			4,675			6,647
Decrease in tax position taken in prior year primarily related to the resolution of tax audit		(1,353	)		(28	)		(1,877	)

Balance, end of year		5,639			10,286			15,056

At December 31, 2017, the Company had US$15,056 thousand of unrecognized tax benefits that if recognized would affect the effective tax rate. For the years ended December 31, 2015, 2016 and 2017, the total amount of interest expense and penalties related to uncertain tax positions recorded in the provision for income tax expense was approximately US$363 thousand, US$575 thousand and US$617 thousand, respectively. The total amount of accrued interest and penalties recognized as of December 31, 2016 and 2017 was US$2,587 thousand and US$3,421 thousand, respectively. The Company does not expect uncertain tax positions to change in the next twelve months, except in the case of settlements with tax authorities, the likelihood and timing of which are difficult to estimate.

The Company files income tax returns in United States and foreign jurisdictions. The following table summarizes the Company’s major jurisdictions and tax year that remain subject to examination by tax authorities as of December 31, 2017:


Tax Jurisdiction		Tax Years
China		2014 and onward
Hong Kong		2014 and onward
Taiwan		2012 and onward
Korea		2012 and onward
United States		2012 onward

Shareholders' Equity

12 Months Ended

Dec. 31, 2017

Shareholders' Equity

16. SHAREHOLDERS’ EQUITY

Appropriations from Earnings

In accordance with the amendments to the Company Act of the ROC in May 2015, the recipients of dividends and bonuses are limited to shareholders and do not include employees. The board of directors of SMI Taiwan held their meeting on June 29, 2016 and, in that meeting, had resolved amendments to the Company’s Articles of Incorporation of SMI Taiwan, particularly the amendment to the policy on dividend distribution and the addition of the policy on distribution of employees’ compensation.

Under the dividend policy of SMI Taiwan as set forth in the amended Articles, SMI Taiwan, the Company’s largest subsidiary, must make appropriations from annual earnings to non-distributable reserve which could affect the Company’s ability to pay cash or stock dividends, if any. SMI Taiwan subsidiary may only distribute dividends after it has made allowances as determined under ROC GAAP at each year-end for:

Payment of taxes;

Recovery of prior years’ deficits, if any;

10% of remaining balance after deduction for a and b as legal reserve;

Special reserve based on relevant laws or regulations or 10% of remaining balance for deduction from above a to c as special reserve when necessary.

Dividends

The Company declared cash dividends per ordinary share during the periods presented as follows:


	2016				2017
	Dividends Per Share (US$)		Amount (in US$ thousands)		Dividends Per Share (US$)		Amount (in US$ thousands)
First quarter	$	0.0375	$	5,290	$	0.050	$	7,134
Second quarter	$	0.0375		5,290	$	0.050		7,148
Third quarter	$	0.0375		5,297	$	0.050		7,155
Fourth quarter	$	0.0500		7,065	$	0.075		10,737

			$	22,942			$	32,174

On October 24, 2016 and October 24, 2017, our Board of Directors, instead of declaring a quarterly dividend, declared an annual dividend of US$0.8 and US$1.2 per ADS, equivalent to US$0.2 and US$0.3 per ordinary share, which will be paid in four quarterly installments starting in the fourth quarter of 2016 and 2017, respectively. Future dividends, if any, on the Company’s outstanding ADSs and ordinary shares will be declared by and subject to the discretion of the Company’s board of directors. If the Company’s board of directors decides to distribute dividends, the form, frequency and amount of such dividends will depend upon the Company’s future operations and earnings, capital requirements and surplus, general financial condition, contractual restrictions and other factors our board of directors may deem relevant.

Any future dividend the Company declares will be paid to the holders of ADSs, subject to the terms of the deposit agreement, to the same extent as holders of the Company’s ordinary shares, to the extent permitted by applicable laws and regulations, less the fees and expenses payable under the deposit agreement. Any dividend the Company declares will be distributed by the depositary bank to the holders of our ADSs. Cash dividends on our ordinary shares, if any, will be paid in U.S. dollars.

Equity Incentive Plan

12 Months Ended

Dec. 31, 2017

Equity Incentive Plan

17. EQUITY INCENTIVE PLAN

2005 Equity Incentive Plan and 2015 Equity Incentive Plan

On April 22, 2005, the Company adopted its 2005 Equity Incentive Plan (“the 2005 Plan”). The 2005 Plan provides for the grant of stock options, stock bonuses, restricted stock awards, restricted stock units and stock appreciation rights, which may be granted to employees (including officers), directors and consultants. The 2005 Plan reserved 10,000 thousand shares of ordinary shares, inclusive of the number of assumed share options under the 2004 Plan, for issuance upon the exercise of stock options.

In 2006, the Company amended the 2005 Plan to reserve an additional 15,000 thousand ordinary shares for issuance upon exercise of stock options and restricted stock units. In 2009, the Company amended the Plan to reserve an additional 15,000 thousand ordinary shares for issuance upon exercise of stock options and restricted stock units.

Restricted stock units are converted into shares of the Company’s ordinary shares upon vesting on one-for-one basis. The vesting of restricted stock unit is subject to the employee’s continuing service to the Company. The cost of these awards is determined using the fair value of the Company’s ordinary share on the date of the grant, and compensation is recognized on a straight-line basis over the requisite service period. The Company’s restricted stock units are considered non-vested share awards as defined under ASC 718.

In April 2010, the Company’s Board of Directors and Compensation Committee approved an employee stock option exchange program that required certain employees to exchange eligible stock options for a lesser number of new stock options that have approximately the same fair values as the options surrendered. Eligible options included stock options granted between August 17, 2005 and July 31, 2008 that had an exercised price above US$1.85. In 2010, 4,369 thousand eligible stock options were exchanged for 3,785 thousand new stock options granted. The new stock options have an exercise price of US$1.47, which was equal to the market price of the Company’s ordinary share on April 26, 2010, the date eligible stock options were surrendered and new stock options granted. The new stock options were issued under the 2005 Plan and are subject to its terms and conditions. The new stock options will continue to vest according to the original vesting schedule. Using the Black-Scholes option pricing model, the Company determined that the fair value of the surrendered stock options on a grant-by-grant basis was approximately equal, as of the date of the exchange, to the fair value of the new stock options granted, resulting in insignificant incremental share-based compensation.

On June 3, 2015, the Company adopted its 2015 Equity Incentive Plan (“the 2015 Plan”). The 2015 Plan provides for the grant of stock options, stock bonuses, restricted stock awards, restricted stock units and stock appreciation rights, which may be granted to employees (including officers), directors and consultants. The 2015 Plan reserved 20,000 thousand shares of ordinary shares for issuance upon exercise of stock options and restricted stock units.

Stock Option and Restricted Stock Units Activity

The following is a summary of, the 2005 Plan and the 2015 Plan, which includes stock options and restricted stock units:


	Unit (in Thousands)
Available for grant at January 1, 2015		1,687
Authorized		20,000
Restricted stock units granted		(2,000	)
Option and restricted stock units forfeited		175

Available for grant at December 31, 2015		19,862
Restricted stock units granted		(1,446	)
Option and restricted stock units forfeited		335

Available for grant at December 31, 2016		18,751
Restricted stock units granted		(1,391	)
Option and restricted stock units forfeited		27

Available for grant at December 31, 2017		17,387

Stock Options

A summary of the stock option activity and related information is as follows:


	Number of Options Shares (in Thousands)			Weighted Average Exercise Price (US$)		Weighted Average Remaining Contractual Life (Years)
Outstanding at January 1, 2015		1,058			1.47
Options forfeited		(143	)		1.47
Options exercised		(336	)		1.47

Outstanding at December 31, 2015		579			1.47		0.92

Options vested and expected to vest after December 31, 2015		579			1.47		0.92
Options forfeited		(257	)		1.47
Options exercised		(64	)		1.47

Outstanding at December 31, 2016		258			1.47		0.25

Options vested and expected to vest after December 31, 2016		258			1.47		0.25
Options exercised		(258	)		1.47

Outstanding at December 31, 2017		—			—		—

No stock options were granted in 2015, 2016 and 2017. The intrinsic value of options exercised, determined as of the date of option exercise, was US$3,688 thousand, US$580 thousand and US$3,040 thousand in 2015, 2016 and 2017, respectively.

As of December 31, 2017, total unrecognized compensation cost related to non-vested share-based compensation awards granted under the Company’s stock option plans, net of estimated forfeitures, was nil.

The aggregate intrinsic value represents the total intrinsic value (the difference between the Company’s closing stock price on the last trading day of fiscal year 2017 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on December 31, 2017. Intrinsic value will change in future periods based on the fair market value of the Company’s stock and the number of shares outstanding.

The total cash received from employees as a result of employee stock option exercises were US$494 thousand, US$93 thousand and US$380 thousand for the years ended December 31, 2015, 2016 and 2017, respectively.

The related tax effect for stock-based compensation benefit were US$561 thousand, US$37 thousand, and US$124 thousand for 2015, 2016 and 2017, respectively. The related tax effect for stock-based compensation expense for option and restricted stock units exercised during 2015, 2016 and 2017 was US$1,647 thousand, US$1,702 thousand and US$2,273 thousand, respectively. The related tax effect was determined using the applicable tax rates in jurisdictions to which this expense relates.

Restricted Stock Units

A summary of the status of restricted stock units and changes is as follows:


	Number of Non-vested Stock Units (in Thousands)			Weighted Average Grant Date Fair Value (US$)		Weight Average Remaining Recognition Period (Years)
Non-vested at January 1, 2015		2,160			4.90		0.31
Restricted stock units granted		2,000			6.83
Restricted stock units vested		(2,003	)		4.96
Restricted stock units forfeited		(32	)		5.85

Non-vested at December 31, 2015		2,125			6.65		0.73
Restricted stock units granted		1,446			12.67
Restricted stock units vested		(1,726	)		6.46
Restricted stock units forfeited		(78	)		6.57

Non-vested at December 31, 2016		1,767			11.65		0.47
Restricted stock units granted		1,391			10.75
Restricted stock units vested		(1,593	)		12.08
Restricted stock units forfeited		(27	)		10.69

Non-vested at December 31, 2017		1,538			10.36		0.33

As of December 31, 2017, there was US$4,736 thousand of total unrecognized compensation cost related to restricted stock units granted under the 2005 Plan and the 2015 Plan.

Stock-based Compensation Expense

The following table shows total stock-based compensation expense included in the Consolidated Statements of Income for the years ended December 31, 2015, 2016 and 2017.


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Cost of sales		261		400		293
Research and development		6,565		10,529		9,255
Sales and marketing		1,790		3,122		3,167
General and administrative		1,802		3,313		2,779

		10,418		17,364		15,494

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies

18. COMMITMENTS AND CONTINGENCIES

FCI provided their employees with collateral for personal loans which is deposited at a designated bank and the amount deposited was US$415 thousand and US$468 thousand at December 31, 2016 and 2017, respectively. Such amounts were accounted for as restricted cash.

Operating Leases

The Company entered into various operating lease agreements for office space that expire on various dates through March 2022. The Company recognized rent expense for the years ended December 31, 2015, 2016 and 2017 of US$2,453 thousand, US$2,595 thousand and US$3,131 thousand, respectively. The minimum operating lease payments expected under these leases as of December 31, 2017 were US$3,711 thousand, US$3,070 thousand, US$1,541 thousand, US$1,159 thousand, and US$65 thousand for the years ending December 31, 2018, 2019, 2020, 2021 and 2022, respectively.

Litigation

The Company is subject to legal proceedings and claims, either asserted or unasserted, which arise in the ordinary course of business. Although the outcome of such proceedings and claims cannot be predicted with certainty, management does not believe that the outcome of any of these matters will have a material adverse effect on our business, results of operations, financial position or cash flows. Any litigation, however, involves potential risk and potentially significant litigation costs, and therefore there can be no assurance that any litigation which is now pending or which may arise in the future would not have such a material adverse effect on our business, financial position, results of operations or cash flows.

All American Semiconductor, Inc. (“All American” or “AASI”) was a former distributor for the Company. On April 25, 2007, All American filed for Chapter 11 bankruptcy protection. At the time of the filing, the Company had US$256 thousand of unpaid accounts receivable from All American. On April 17, 2009 SMI USA and related entities were named as defendants in an adversary proceeding filed by the AASI Creditor Liquidating Trust (“CLT”) in the bankruptcy case pending in the U.S. Bankruptcy Court for the Southern District of Florida. The CLT was seeking the return of allegedly avoidable transfers in the amount of US$854 thousand. SMI USA filed an answer and affirmative defenses. In March 2010, SMI USA settled with the CLT by paying the amount of US$220 thousand and on April 1, 2010, the Bankruptcy Court granted the motion to approve stipulations to compromise controversy. On August 23, 2010, the Court entered an order dismissing the adversary proceeding. In June 2011, Liquidating Trustee for the CLT filed the AASI Creditor Liquidating Trustee’s Seventeenth Omnibus Objection to Claims but in August 2011, withdrew it with respect to SMI USA’s proof of claim. As a holder of allowed claims, we are entitled to receive distribution pursuant to the bankruptcy plan. On December 31, 2017, we received total distributions of US$265 thousand from the CLT. We are not expecting further distributions.

Segment Information

12 Months Ended

Dec. 31, 2017

Segment Information

19. SEGMENT INFORMATION

The Company is the global leader and pioneer in developing NAND flash controllers for solid storage devices. The Company currently operates as one reportable segment. The chief operating decision maker is the Chief Executive Officer.

The Company groups its products into three categories, based on the markets in which they may be used. The following summarizes the Company’s revenue by product category:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Mobile Storage		302,910		510,687		480,735
Mobile Communications		50,896		39,322		37,447
Others		7,491		6,137		5,222

		361,297		556,146		523,404

Revenue is attributed to a geographic area based on the bill-to location. The following summarizes the Company’s revenue by geographic area:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Taiwan		71,387		75,926		72,768
United States		39,558		59,390		40,344
Japan		19,636		17,070		18,797
Korea		150,118		183,249		176,813
China		69,623		151,112		126,048
Others		10,975		69,399		88,634

	361,297		556,146		523,404

Major customers representing at least 10% of net sales


	Year Ended December 31
	2015				2016				2017
	US$		%		US$		%		US$		%
SK Hynix		108,645		30		156,541		28		150,762		29
Intel		*		*		*		*		50,205		10

*	Less than 10%

Long-lived assets (property and equipment, net) by geographic area were as follows:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Taiwan		32,014		34,011		36,369
United States		274		237		242
Korea		1,891		1,448		1,936
China		16,268		12,181		12,798
Japan		22		15		25

	50,469		47,892		51,370

Fair Value Measurement

12 Months Ended

Dec. 31, 2017

Fair Value Measurement

20. FAIR VALUE MEASUREMENT

The following section describes the valuation methodologies the Company uses to measure assets and liabilities at fair value.

The Company uses quoted prices in active markets for identical assets to determine fair value where applicable. This pricing methodology applies to Level 1 investments such as bond funds. The fair value of the principal protected notes was determined by its present value utilizing rate of return as the market observable input and therefore, these are classified as Level 2 instruments. This is because there generally are no quoted prices in active markets for identical principal protected notes at the reporting date. Hence, in order to determine the fair value, the Company must use observable inputs other than quoted prices in active markets for identical or similar instruments, quoted prices for similar instruments in active markets, or other inputs that are observable.

For the years ended December 31, 2016 and 2017, none of the Company’s assets measured on a recurring basis was determined by using significant unobservable inputs.

The following table presents our assets measured at fair value on a recurring basis as of December 31, 2016 and 2017:

December 31, 2016

Level 1

Level 2

Level 3

Total

US$

Assets

Short-term investments — trading securities

695

2,607

—

3,302

December 31, 2017

Level 1

Level 2

Level 3

Total

US$

Assets

Short-term investments — trading securities

755

6,186

—

6,941

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Basis of Presentation

Basis of Presentation

Use of Estimates

Use of Estimates

Concentration of Credit Risk and Significant Customers

Concentration of Credit Risk and Significant Customers

Fair Value of Financial Instruments

Fair Value of Financial Instruments

Level 1 — Use unadjusted quoted prices in active markets for identical assets or liabilities.

Level 3 — Use inputs that are generally unobservable and reflect the use of significant management judgments and estimates.

See Note 20, “Fair Value Measurement”, for the related disclosure.

Cash Equivalents

Cash Equivalents

Short-term Investments

Short-term Investments

Allowance for Doubtful Receivables

Allowance for Doubtful Receivables

Inventories

Inventories

Long-term Investments

Long-term Investments

Noncurrent Assets Held for Sale

Noncurrent Assets Held for Sale

Property and Equipment

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation. Significant additions, renewals and betterments are capitalized, while maintenance and repairs are expensed as incurred.

Government Grants

Government Grants

Goodwill and Intangible Assets

Goodwill and Intangible Assets

Impairment of Goodwill and Long-Lived Assets

Impairment of Goodwill and Long-Lived Assets

Other Assets

Other Assets

Other assets primarily consist of industrial property right and deposits for office leases.

Restricted Assets

Restricted Assets

Bank loans

Bank loans

Loans from financial institutions are stated at the amount of unpaid principal. Bank loans comprise borrowings which are held by banks based in Taiwan.

Other long-term liabilities

Other long-term liabilities

Other long-term liabilities primarily consist of payable to former shareholders of Shannon Systems and unrecognized tax benefit.

Pension Costs

Pension Costs

Revenue Recognition

Revenue Recognition

Research and Development

Research and Development

Income Taxes

Income Taxes

Foreign Currency Transactions

Foreign Currency Transactions

Translation of Foreign Currency Financial Statements

Translation of Foreign Currency Financial Statements

Comprehensive Income (Loss)

Comprehensive Income (Loss)


	Year Ended December 31, 2015									Year Ended December 31, 2016									Year Ended December 31, 2017
	US$									US$									US$
	Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)
Beginning balance		3,354			(849	)		2,505			1,486			(853	)		633			(69	)		(963	)		(1,032	)
Current-period change		(1,868	)		(4	)		(1,872	)		(1,555	)		(110	)		(1,665	)		3,390			285			3,675

Ending balance		1,486			(853	)		633			(69	)		(963	)		(1,032	)		3,321			(678	)		2,643

Legal Contingencies

Legal Contingencies

Earnings Per Share

Earnings Per Share

Stock-Based Compensation

Stock-Based Compensation

Dividends

Dividends

Recent Accounting Pronouncements

Recent Accounting Pronouncements

The following table reflects the adjustments made to the consolidated statements of cash flows to confirm prior period classifications under the new guidance for the periods presented:


	As Reported			Adjustment			As Adjusted
	US$			US$			US$
Year Ended December 31, 2014:
Net cash provided by operating activities		68,725			—			68,725
Net cash provided by (used in) investing activities		(15,413	)		3,817			(11,596	)
Net cash used in financing activities		(19,710	)		—			(19,710	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		33,602			3,817			37,419
Effect of exchange rate changes		(1,111	)		—			(1,111	)
Cash, cash equivalents, and restricted cash* at beginning of year		161,720			17,864			179,584

Cash, cash equivalents, and restricted cash* at end of year		194,211			21,681			215,892

Year Ended December 31, 2015:
Net cash provided by operating activities		65,946			—			65,946
Net cash used in investing activities		(58,414	)		(44	)		(58,458	)
Net cash used in financing activities		(20,271	)		—			(20,271	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		(12,739	)		(44	)		(12,783	)
Effect of exchange rate changes		(953	)		—			(953	)
Cash, cash equivalents, and restricted cash* at beginning of year		194,211			21,681			215,892

Cash, cash equivalents, and restricted cash* at end of year		180,519			21,637			202,156

*	The restricted cash is only included in the amount of “as adjusted” item.


	As of December 31
	2014		2015		2016		2017
	US$		US$		US$		US$
Cash and cash equivalents		194,211		180,519		274,483		359,453
Restricted cash included in restricted assets-current		19,322		19,328		44,393		19,515
Restricted cash included in other assets		2,359		2,309		2,301		2,555

Total cash, cash equivalents, and restricted cash shown in the statements of cash flows		215,892		202,156		321,177		381,523

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Components of Accumulated Other Comprehensive Income (Loss)

The following table presents the components of accumulated other comprehensive income (loss) as of December 31, 2015, 2016 and 2017:


	Year Ended December 31, 2015									Year Ended December 31, 2016									Year Ended December 31, 2017
	US$									US$									US$
	Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)			Foreign currency items			Defined benefit pension plans			Accumulated other comprehensive income (loss)
Beginning balance		3,354			(849	)		2,505			1,486			(853	)		633			(69	)		(963	)		(1,032	)
Current-period change		(1,868	)		(4	)		(1,872	)		(1,555	)		(110	)		(1,665	)		3,390			285			3,675

Ending balance		1,486			(853	)		633			(69	)		(963	)		(1,032	)		3,321			(678	)		2,643

Revised Previously Reported Consolidated Statements of Cash Flows

The following table reflects the adjustments made to the consolidated statements of cash flows to confirm prior period classifications under the new guidance for the periods presented:


	As Reported			Adjustment			As Adjusted
	US$			US$			US$
Year Ended December 31, 2014:
Net cash provided by operating activities		68,725			—			68,725
Net cash provided by (used in) investing activities		(15,413	)		3,817			(11,596	)
Net cash used in financing activities		(19,710	)		—			(19,710	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		33,602			3,817			37,419
Effect of exchange rate changes		(1,111	)		—			(1,111	)
Cash, cash equivalents, and restricted cash* at beginning of year		161,720			17,864			179,584

Cash, cash equivalents, and restricted cash* at end of year		194,211			21,681			215,892

Year Ended December 31, 2015:
Net cash provided by operating activities		65,946			—			65,946
Net cash used in investing activities		(58,414	)		(44	)		(58,458	)
Net cash used in financing activities		(20,271	)		—			(20,271	)

Net increase (decrease) in cash, cash equivalents, and restricted cash*		(12,739	)		(44	)		(12,783	)
Effect of exchange rate changes		(953	)		—			(953	)
Cash, cash equivalents, and restricted cash* at beginning of year		194,211			21,681			215,892

Cash, cash equivalents, and restricted cash* at end of year		180,519			21,637			202,156

*	The restricted cash is only included in the amount of “as adjusted” item.

Reconciliation of Cash Cash Equivalents and Restricted cash


	As of December 31
	2014		2015		2016		2017
	US$		US$		US$		US$
Cash and cash equivalents		194,211		180,519		274,483		359,453
Restricted cash included in restricted assets-current		19,322		19,328		44,393		19,515
Restricted cash included in other assets		2,359		2,309		2,301		2,555

Total cash, cash equivalents, and restricted cash shown in the statements of cash flows		215,892		202,156		321,177		381,523

Business Acquisition (Tables)

12 Months Ended

Dec. 31, 2017

Shannon Systems

Estimated Fair Values of Assets Acquired and Liabilities Assumed

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition:


	US$
Cash, cash equivalents and restricted cash		1,904
Accounts receivable, net		946
Inventories		2,624
Other current assets		288
Property and equipment		71
Goodwill		33,204
Identifiable intangible assets		8,381
Accounts payable		(644	)
Accrued expenses and other current liabilities		(1,209	)

Net assets acquired		45,565

Identifiable Intangible Assets and Useful Lives

The identifiable intangible assets and respective useful lives are as follows:


	US$		Useful Life
Developed technology		3,789		3.5
In-process research and development (“IPR&D”)		4,592		indefinite

Total identifiable intangible assets		8,381

Results of Acquired Entity Included on Consolidated Statement of Income

The results of Shannon Systems since the acquisition date included on the consolidated statement of income for the year ended December 31, 2015 were as follows:


	US$
Net sales		9,049
Net income		421

Unaudited Proforma Information of Summary of Results of Operations

The following unaudited pro forma information represents a summary of the results of operations as if the acquisition occurred on January 1, 2014 and 2015 and includes certain pro forma adjustments, including amortization of identifiable intangibles from that date (in thousands except earnings per share):


	Year Ended December 31
	2014		2015
Net sales		293,562		364,670
Net income		42,483		58,468
Earnings per share
Basic		0.31		0.42
Diluted		0.31		0.42
Weighted average ordinary shares outstanding (thousand)
Basic		136,164		138,880
Diluted		138,347		140,414

Bigtera

Estimated Fair Values of Assets Acquired and Liabilities Assumed

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the date of acquisition:


	US$
Cash, cash equivalents and restricted cash		78
Accounts receivable, net		380
Other current assets		14
Property and equipment		15
Goodwill		625
Identifiable intangible assets		4,736
Accounts payable		(436	)
Accrued expenses and other current liabilities		(748	)

Net assets acquired		4,664

Identifiable Intangible Assets and Useful Lives

The identifiable intangible assets and respective useful lives are as follows:


	US$		Useful Life
Know-how		3,753		5.5
Current technology		983		5.5

Total identifiable intangible assets		4,736

Results of Acquired Entity Included on Consolidated Statement of Income

The results of Bigtera since the acquisition date included on the consolidated statement of income for the year ended December 31, 2017 were as follows:


	US$
Net sales		2,993
Net income		(314	)

Unaudited Proforma Information of Summary of Results of Operations

The following unaudited pro forma information represents a summary of the results of operations as if the acquisition occurred on January 1, 2016 and 2017 and includes certain pro forma adjustments, including amortization of identifiable intangibles from that date (in thousands except earnings per share):


	Year Ended December 31
	2016		2017
Net sales		557,672		523,849
Net income		109,736		73,834
Earnings per share
Basic		0.78		0.52
Diluted		0.77		0.51
Weighted average ordinary shares outstanding (thousand)
Basic		140,919		142,738
Diluted		142,050		143,606

Cash, Cash Equivalents, and Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2017

Details of Cash, Cash Equivalents, and Restricted Cash


	December 31
	2016		2017
	US$		US$
Cash and deposits in bank		58,391		59,751
Time deposits		199,064		269,392
Bonds acquired under repurchase agreements		17,028		30,310

Total cash and cash equivalents		274,483		359,453
Restricted cash (Note 2)		46,694		22,070

	321,177		381,523

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2017

Short Term Investments


	December 31
	2016		2017
	US$		US$
Trading securities		3,302		6,941

Notes and Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Notes and Accounts Receivable


	December 31
	2016			2017
	US$			US$
Trade accounts receivable		75,946			81,165
Allowance for doubtful accounts		(723	)		(598	)
Allowance for sales returns and discounts		(1,624	)		(1,432	)

	73,599			79,135

Changes in Allowances

The changes in the allowances are summarized as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Allowances for doubtful accounts
Balance, beginning of year		1,167			775			723
Reversals charged to expense, net		(392	)		(12	)		(125	)
Write-offs		—			(40	)		—

Balance, end of year		775			723			598


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Allowances for sales returns and discounts
Balance, beginning of year		1,427			1,555			1,624
Additions charged to expense, net		1,753			3,285			3,093
Actual sales return and discount		(1,625	)		(3,216	)		(3,285	)

Balance, end of year		1,555			1,624			1,432

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Components of Inventory

The components of inventories are as follows:


	December 31
	2016		2017
	US$		US$
Finished goods		24,782		41,365
Work in process		31,185		25,090
Raw materials		15,920		27,731

		71,887		94,186

Long-Term Investments (Tables)

12 Months Ended

Dec. 31, 2017

Long-Term Investments

As of December 31, 2016 and 2017, the Company held equity investments in several privately-held companies with the carrying value as follows:


	Percentage of Ownership						December 31
	2016			2017			2016		2017
							US$		US$
Cost method:
Cashido Corp. (Cashido)		2.1	%		2.1	%		91		—
Vastview Technology, Corp. (Vastview)		2.9	%		2.9	%		29		—

								120		—

Noncurrent Assets Held for Sale (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Noncurrent Assets Held for Sale


	December 31
	2016		2017
	US$		US$
Assets held for sale		3,363		—

		3,363		—

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property and Equipment

December 31
	2016		2017
	US$		US$
Cost:
Land		9,309		9,309
Buildings		29,232		30,288
Machinery and equipment		18,122		21,665
Furniture and fixtures		6,760		7,746
Leasehold and buildings improvement		4,911		5,497
Software		22,745		24,864

Total		91,079		99,369

Accumulated depreciation:
Buildings		2,708		3,472
Machinery and equipment		14,032		15,665
Furniture and fixtures		4,207		5,212
Leasehold and buildings improvement		3,591		4,213
Software		19,130		19,874

		43,668		48,436
Prepayment and construction in progress		481		437

		47,892		51,370

Goodwill and Acquired Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Intangible Assets Acquired from Acquisition

December 31
	2016									2017
	US$									US$
	Cost		Accumulated Impairment		Accumulated Amortization			Net Carrying Amount		Cost		Accumulated Impairment		Accumulated Amortization			Net Carrying Amount
Acquisition-related intangible assets		8,381		—		(3,154	)		5,227		13,117		—		(5,688	)		7,429

Schedule of Goodwill

December 31
	2016										2017
	US$										US$
	Cost		Accumulated Impairment			Foreign Currency Adjustment			Net Carrying Amount		Cost		Accumulated Impairment			Foreign Currency Adjustment			Net Carrying Amount
Goodwill		99,504		(30,808	)		(40	)		68,656		100,129		(41,145	)		(20	)		58,964

Short-Term Bank Loans (Tables)

12 Months Ended

Dec. 31, 2017

Short-Term Bank Loans


	December 31
	2016		2017
	US$		US$
Secured loans		25,000		25,000

	25,000		25,000

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Accrued Expenses and Other Current Liabilities


	December 31
	2016		2017
	US$		US$
Wages and bonus		29,028		29,629
Dividends		21,382		32,451
Research and development payable		5,456		5,638
License fees and royalties		4,021		3,729
Professional fees		2,038		2,286
Equipment		492		1,844
Others		6,319		8,186

	68,736		83,763

Pension Plan (Tables)

12 Months Ended

Dec. 31, 2017

Changes in Benefits Obligation and Plan Assets and Reconciliation of Funded Status

The changes in benefits obligation and plan assets and the reconciliation of funded status are as follows:


	December 31
	2015			2016			2017
	US$			US$			US$
Change in benefit obligation
Projected benefit obligation at beginning of year		3,320			3,632			4,242
Service cost		273			487			1,572
Interest cost		57			104			336
Actuarial loss (gain)		79			151			(665	)
Benefits paid		(97	)		(132	)		(354	)

Projected benefit obligation at end of year		3,632			4,242			5,131

Change in plan assets
Fair value of plan assets at beginning of year		2,556			2,800			3,902
Actual return on plan assets		33			33			81
Employer contributions		328			1,203			1,358
Benefits paid		(117	)		(134	)		(227	)

Fair value of plan assets at end of year		2,800			3,902			5,114

Funded status recognized as an other asset (liabilities)		(832	)		(340	)		(17	)

Amounts Recognized in Accumulated Other Comprehensive Income

Amounts recognized in accumulated other comprehensive income consist of the following:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Net loss		852		963		678
Transition obligation		1		—		—

Total recognized in accumulated other comprehensive income		853		963		678

Components of Net Periodic Benefit Cost

The components of net periodic benefit cost are as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Service cost		273			487			1,572
Interest cost		57			104			336
Projected return on plan assets		(47	)		(28	)		(58	)
Amortization of unrecognized net transition obligation and unrecognized net actuarial gain		27			11			37

Net periodic benefit cost		310			574			1,887

Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Loss

Other changes in plan assets and benefit obligation recognized in other comprehensive loss:


	2015		2016			2017
	US$		US$			US$
Recognize the decrease in net gain (loss)		4		111			(285	)
Amortization of net gain (loss)		—		(1	)		—

Total recognized in other comprehensive loss (income)		4		110			(285	)

Expected Benefit Payments

Expected benefit payments:


	US$
2018		188
2019		184
2020		407
2021		181
2022		182
2023 and thereafter		2,057

Actuarial Assumptions to Determine Benefit Obligations

The actuarial assumptions to determine the benefit obligations were as follows:


	2015						2016						2017
	Taiwan			Korea			Taiwan			Korea			Taiwan			Korea
Weighted-average assumptions used to determine benefit obligations:
Discount rate		1.75	%		3.90	%		1.50	%		3.80	%		1.63	%		4.10	%
Rate of compensation increase		4.25	%		4.00	%		4.25	%		3.50	%		4.25	%		3.50	%
Weighted-average assumptions used to determine net projected benefit cost:
Discount rate		1.75	%		3.90	%		1.50	%		3.80	%		1.63	%		4.10	%
Expected long-term return on plan assets		2.00	%		1.20	%		2.00	%		1.10	%		1.75	%		1.10	%
Rate of compensation increase		4.25	%		4.00	%		4.25	%		3.50	%		4.25	%		3.50	%

Fair Values of FCI's Pension Plan Assets

The fair values of FCI’s pension plan assets at December 31, 2016 and 2017 are as follows:


	December 31
	2016		2017
	US$		US$
Guaranteed interest contract
Kyobo Life Insurance Co. Ltd.		1,284		1,599
Shinhan Investment Co. .		—		374
Fixed deposit
Industrial Bank of Korea		1,537		1,892

		2,821		3,865

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Components of Income Tax Expense

The components of income tax expense are as follows:


	Year Ended December 31
	2015		2016			2017
	US$		US$			US$
Current		17,338		31,063			23,465
Deferred		911		(3,373	)		581

Income tax expense		18,249		27,690			24,046

Income (Loss) Before Income Taxes for Domestic and Foreign Entities

The income (loss) before income taxes for domestic and foreign entities is as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Domestic		(12,037	)		(20,663	)		(27,902	)
Foreign		90,537			159,293			126,903

		78,500			138,630			99,001

Reconciliation of Income Tax Expense on Pretax Income at Statutory Rate and Income Tax Expense

The Company and its subsidiaries file separate income tax returns. A reconciliation of income tax expense on pretax income at statutory rate and income tax expense is shown below:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Tax expense at statutory rate of Cayman		—			—			—
Differences between Cayman and foreign statutory tax rates		18,765			34,415			24,255
Tax-exempt income		(906	)		(4,648	)		—
Permanent differences		(1,065	)		(7,792	)		(4,249	)
Temporary differences		(330	)		(1,533	)		(1,445	)
Alternative minimum tax		4			594			4
Income tax (10%) on undistributed earnings		2,460			5,677			2,709
Net changes in income tax credit		(897	)		(495	)		166
Net changes in valuation allowance of deferred income tax assets		1,621			1,724			(2,401	)
Net operating loss carryforwards		(2,052	)		(1,689	)		1,492
Liabilities related to unrealized tax benefits		672			2,385			3,455
Adjustment of prior years’ taxes and others		(23	)		(948	)		60

Income tax expense		18,249			27,690			24,046

Deferred Income Tax Assets (Liabilities)

Deferred income tax assets (liabilities) are as follows:


	December 31
	2016			2017
	US$			US$
Notes and accounts receivable		44			44
Stock-based compensation		1,146			771
Allowance for sales return		205			154
Inventory reserve		1,646			1,311
Foreign currency translation		2			( 5	)
Property and equipment		383			168
Investment tax credits		8,647			9,078
Net operating loss carryforwards		12,335			10,391
Others		411			562
Valuation allowance		(20,836	)		(19,072	)

		3,983			3,402

Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending balances of the total amounts of unrecognized tax benefits is as follows:


	Year Ended December 31
	2015			2016			2017
	US$			US$			US$
Balance, beginning of year		4,655			5,639			10,286
Increases in tax positions taken in current year		2,337			4,675			6,647
Decrease in tax position taken in prior year primarily related to the resolution of tax audit		(1,353	)		(28	)		(1,877	)

Balance, end of year		5,639			10,286			15,056

Summary of Major Jurisdictions and Tax Year Subject to Examination by Tax Authorities

The following table summarizes the Company’s major jurisdictions and tax year that remain subject to examination by tax authorities as of December 31, 2017:


Tax Jurisdiction		Tax Years
China		2014 and onward
Hong Kong		2014 and onward
Taiwan		2012 and onward
Korea		2012 and onward
United States		2012 onward

Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Cash Dividends Declared Per Ordinary Share

The Company declared cash dividends per ordinary share during the periods presented as follows:


	2016				2017
	Dividends Per Share (US$)		Amount (in US$ thousands)		Dividends Per Share (US$)		Amount (in US$ thousands)
First quarter	$	0.0375	$	5,290	$	0.050	$	7,134
Second quarter	$	0.0375		5,290	$	0.050		7,148
Third quarter	$	0.0375		5,297	$	0.050		7,155
Fourth quarter	$	0.0500		7,065	$	0.075		10,737

			$	22,942			$	32,174

Equity Incentive Plan (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Stock Option and Restricted Stock Units Activity

The following is a summary of, the 2005 Plan and the 2015 Plan, which includes stock options and restricted stock units:


	Unit (in Thousands)
Available for grant at January 1, 2015		1,687
Authorized		20,000
Restricted stock units granted		(2,000	)
Option and restricted stock units forfeited		175

Available for grant at December 31, 2015		19,862
Restricted stock units granted		(1,446	)
Option and restricted stock units forfeited		335

Available for grant at December 31, 2016		18,751
Restricted stock units granted		(1,391	)
Option and restricted stock units forfeited		27

Available for grant at December 31, 2017		17,387

Summary of Stock Option Activity

A summary of the stock option activity and related information is as follows:


	Number of Options Shares (in Thousands)			Weighted Average Exercise Price (US$)		Weighted Average Remaining Contractual Life (Years)
Outstanding at January 1, 2015		1,058			1.47
Options forfeited		(143	)		1.47
Options exercised		(336	)		1.47

Outstanding at December 31, 2015		579			1.47		0.92

Options vested and expected to vest after December 31, 2015		579			1.47		0.92
Options forfeited		(257	)		1.47
Options exercised		(64	)		1.47

Outstanding at December 31, 2016		258			1.47		0.25

Options vested and expected to vest after December 31, 2016		258			1.47		0.25
Options exercised		(258	)		1.47

Outstanding at December 31, 2017		—			—		—

Summary of Restricted Stock Units and Changes

A summary of the status of restricted stock units and changes is as follows:


	Number of Non-vested Stock Units (in Thousands)			Weighted Average Grant Date Fair Value (US$)		Weight Average Remaining Recognition Period (Years)
Non-vested at January 1, 2015		2,160			4.90		0.31
Restricted stock units granted		2,000			6.83
Restricted stock units vested		(2,003	)		4.96
Restricted stock units forfeited		(32	)		5.85

Non-vested at December 31, 2015		2,125			6.65		0.73
Restricted stock units granted		1,446			12.67
Restricted stock units vested		(1,726	)		6.46
Restricted stock units forfeited		(78	)		6.57

Non-vested at December 31, 2016		1,767			11.65		0.47
Restricted stock units granted		1,391			10.75
Restricted stock units vested		(1,593	)		12.08
Restricted stock units forfeited		(27	)		10.69

Non-vested at December 31, 2017		1,538			10.36		0.33

Stock-based Compensation Expense

The following table shows total stock-based compensation expense included in the Consolidated Statements of Income for the years ended December 31, 2015, 2016 and 2017.


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Cost of sales		261		400		293
Research and development		6,565		10,529		9,255
Sales and marketing		1,790		3,122		3,167
General and administrative		1,802		3,313		2,779

		10,418		17,364		15,494

Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Revenue by Product Category

The Company groups its products into three categories, based on the markets in which they may be used. The following summarizes the Company’s revenue by product category:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Mobile Storage		302,910		510,687		480,735
Mobile Communications		50,896		39,322		37,447
Others		7,491		6,137		5,222

		361,297		556,146		523,404

Revenue by Geographic Area

Revenue is attributed to a geographic area based on the bill-to location. The following summarizes the Company’s revenue by geographic area:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Taiwan		71,387		75,926		72,768
United States		39,558		59,390		40,344
Japan		19,636		17,070		18,797
Korea		150,118		183,249		176,813
China		69,623		151,112		126,048
Others		10,975		69,399		88,634

	361,297		556,146		523,404

Major customers representing at least 10% of net sales


	Year Ended December 31
	2015				2016				2017
	US$		%		US$		%		US$		%
SK Hynix		108,645		30		156,541		28		150,762		29
Intel		*		*		*		*		50,205		10

*	Less than 10%

Long-Lived Assets (Property and Equipment, Net) by Geographic Area

Long-lived assets (property and equipment, net) by geographic area were as follows:


	Year Ended December 31
	2015		2016		2017
	US$		US$		US$
Taiwan		32,014		34,011		36,369
United States		274		237		242
Korea		1,891		1,448		1,936
China		16,268		12,181		12,798
Japan		22		15		25

	50,469		47,892		51,370

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2017

Assets Measured at Fair Value on Recurring Basis

The following table presents our assets measured at fair value on a recurring basis as of December 31, 2016 and 2017:

December 31, 2016

Level 1

Level 2

Level 3

Total

US$

Assets

Short-term investments — trading securities

695

2,607

—

3,302

December 31, 2017

Level 1

Level 2

Level 3

Total

US$

Assets

Short-term investments — trading securities

755

6,186

—

6,941

Organization and Operations - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 Product
Minimum
Organization And Operations [Line Items]
Number of product shipped annually	750,000,000

Summary Of Significant Accounting Policies - Additional Information (Detail) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Customer shares	Dec. 31, 2016 USD ($) Customer shares	Dec. 31, 2015 USD ($) Customer shares
Significant Accounting Policies [Line Items]
Subsidiary ownership percentage	100.00%
Number of customers accounted for 10% or more sales \| Customer	2	1	1
Depreciation and amortization \| $	$ 10,599	$ 9,482	$ 7,936
Warranty period for manufacturing defects of products	1 year
Evaluation of tax benefits realized upon settlement	50.00%
Minimum
Significant Accounting Policies [Line Items]
Short term investment maturity period	3 months
Maximum
Significant Accounting Policies [Line Items]
Short term investment maturity period	1 year
Held-to-maturity investment maturity period	1 year
Net sales \| Customers accounted for 10% or more \| Top Ten Customers [Member]
Significant Accounting Policies [Line Items]
Major customers percentage of net sales	72.00%	75.00%	72.00%
Net sales \| Customers accounted for 10% or more \| One Customer [Member]
Significant Accounting Policies [Line Items]
Major customers percentage of net sales		28.00%	30.00%
Net sales \| Customers accounted for 10% or more \| Two Customers [Member]
Significant Accounting Policies [Line Items]
Major customers percentage of net sales	39.00%
Employee Stock Option And Restricted Stock Units [Member]
Significant Accounting Policies [Line Items]
The effect of dilutive securities of employee stock options and restricted stock units	868	1,131	1,534
Employee Stock Option And Restricted Stock Units [Member] \| American Depositary Shares
Significant Accounting Policies [Line Items]
The effect of dilutive securities of employee stock options and restricted stock units	218	283	384
Software \| Minimum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	1 year
Software \| Maximum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	5 years
Development technology \| Minimum
Significant Accounting Policies [Line Items]
Intangible asset amortized over estimated useful lives	3 years 6 months
Development technology \| Maximum
Significant Accounting Policies [Line Items]
Intangible asset amortized over estimated useful lives	5 years 6 months
Buildings \| Minimum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	25 years
Buildings \| Maximum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	50 years
Machinery and Equipment \| Minimum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	3 years
Machinery and Equipment \| Maximum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	6 years
Furniture and Fixtures \| Minimum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	3 years
Furniture and Fixtures \| Maximum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	8 years
Leasehold And Building Improvement \| Minimum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	2 years
Leasehold And Building Improvement \| Maximum
Significant Accounting Policies [Line Items]
Property plant and equipment estimated useful life	6 years

Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Foreign currency items	$ (69)	$ 1,486	$ 3,354
Current-period change, Foreign currency items	3,390	(1,555)	(1,868)
Ending balance, Foreign currency items	3,321	(69)	1,486
Beginning balance, Defined benefit pension plans	(963)	(853)	(849)
Current-period change, Defined benefit pension plans	285	(110)	(4)
Ending balance, Defined benefit pension plans	(678)	(963)	(853)
Beginning balance, Accumulated other comprehensive income (loss)	(1,032)	633	2,505
Current-period change, Accumulated other comprehensive income (loss)	3,675	(1,665)	(1,872)
Ending balance, Accumulated other comprehensive income (loss)	$ 2,643	$ (1,032)	$ 633

Revised Previously Reported Consolidated Statements of Cash Flows (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Condensed Cash Flow Statements, Captions [Line Items]

Net cash provided by operating activities

$ 103,881

$ 125,568

$ 65,946

$ 68,725

Net cash provided by (used in) investing activities

(14,548)

(8,220)

(58,458)

(11,596)

Net cash provided by (used in) financing activities

(31,740)

2,194

(20,271)

(19,710)

Net increase (decrease) in cash, cash equivalents, and restricted cash

57,593

119,542

(12,783)

^[1]

37,419

^[1]

EFFECT OF EXCHANGE RATE CHANGES

2,753

(521)

(953)

(1,111)

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF YEAR

321,177

202,156

^[1]

215,892

^[1]

179,584

^[1]

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, END OF YEAR

$ 381,523

321,177

202,156

^[1]

215,892

^[1]

As Reported

Condensed Cash Flow Statements, Captions [Line Items]

Net cash provided by operating activities

65,946

68,725

Net cash provided by (used in) investing activities

(58,414)

(15,413)

Net cash provided by (used in) financing activities

(20,271)

(19,710)

Net increase (decrease) in cash, cash equivalents, and restricted cash

^[1]

(12,739)

33,602

EFFECT OF EXCHANGE RATE CHANGES

(953)

(1,111)

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF YEAR

^[1]

180,519

194,211

161,720

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, END OF YEAR

^[1]

180,519

194,211

Adjustment

Condensed Cash Flow Statements, Captions [Line Items]

Net cash provided by (used in) investing activities

(44)

3,817

Net increase (decrease) in cash, cash equivalents, and restricted cash

^[1]

(44)

3,817

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, BEGINNING OF YEAR

^[1]

$ 21,637

21,681

17,864

CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, END OF YEAR

^[1]

$ 21,637

$ 21,681

[1]	The restricted cash is only included in the amount of "as adjusted" item.

Reconciliation of Cash Cash Equivalents and Restricted cash (Detail) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

^[1]

Restricted Cash and Cash Equivalents Items [Line Items]

Cash and cash equivalents

$ 359,453

$ 274,483

$ 180,519

$ 194,211

Restricted cash included in restricted assets-current

19,515

44,393

19,328

19,322

Restricted cash included in other assets

2,555

2,301

2,309

2,359

Total cash ,cash equivalents, and restricted cash

$ 381,523

$ 321,177

$ 202,156

^[1]

$ 215,892

^[1]

$ 179,584

[1]	The restricted cash is only included in the amount of "as adjusted" item.

Business Acquisition - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 03, 2017	Jul. 01, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Other long-term liabilities			$ 22,329	$ 16,910
Shannon Systems
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding shares acquired		100.00%
Business acquisition shares issued, shares		1,560,000
Business acquisition shares issued, value		$ 7,640
Business acquisition, cash paid to acquire interest		$ 37,925
Business acquisition costs					$ 359
Shannon Systems \| Other Noncurrent Liabilities
Business Acquisition [Line Items]
Other long-term liabilities			5,735
Bigtera
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding shares acquired	100.00%
Business acquisition, cash paid to acquire interest	$ 4,664
Business acquisition costs			171
Bigtera \| Other Noncurrent Liabilities
Business Acquisition [Line Items]
Other long-term liabilities			$ 1,721

Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 03, 2017	Dec. 31, 2016	Jul. 01, 2015
Business Acquisition [Line Items]
Goodwill	$ 58,964		$ 68,656
Shannon Systems
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash				$ 1,904
Accounts receivable, net				946
Inventories				2,624
Other current assets				288
Property and equipment				71
Goodwill				33,204
Identifiable intangible assets				8,381
Accounts payable				(644)
Accrued expenses and other current liabilities				(1,209)
Net assets acquired				$ 45,565
Bigtera
Business Acquisition [Line Items]
Cash, cash equivalents and restricted cash		$ 78
Accounts receivable, net		380
Other current assets		14
Property and equipment		15
Goodwill		625
Identifiable intangible assets		4,736
Accounts payable		(436)
Accrued expenses and other current liabilities		(748)
Net assets acquired		$ 4,664

Identifiable Intangible Assets and Useful Lives (Detail) - USD ($) $ in Thousands	Jul. 03, 2017	Jul. 01, 2015
Shannon Systems
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Total identifiable intangible assets		$ 8,381
Shannon Systems \| In Process Research and Development
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets		$ 4,592
Indefinite-live intangible assets useful life		indefinite
Shannon Systems \| Developed Technology
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite-lived intangible assets		$ 3,789
Finite-lived intangible assets useful life		3 years 6 months
Bigtera
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite-lived intangible assets	$ 4,736
Total identifiable intangible assets	4,736
Bigtera \| Know How Technology
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite-lived intangible assets	$ 3,753
Finite-lived intangible assets useful life	5 years 6 months
Bigtera \| Current Technology
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite-lived intangible assets	$ 983
Finite-lived intangible assets useful life	5 years 6 months

Results of Acquired Entity Included on Consolidated Statement of Income (Detail) - USD ($) $ in Thousands	6 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Shannon Systems
Business Acquisition Information [Line Items]
Net sales		$ 9,049
Net income		$ 421
Bigtera
Business Acquisition Information [Line Items]
Net sales	$ 2,993
Net income	$ (314)

Unaudited Pro forma Information of Summary of Results of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shannon Systems
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net sales			$ 364,670	$ 293,562
Net income			$ 58,468	$ 42,483
Earnings per share
Basic			$ 0.42	$ 0.31
Diluted			$ 0.42	$ 0.31
Weighted average ordinary shares outstanding (thousand)
Basic			138,880	136,164
Diluted			140,414	138,347
Bigtera
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Net sales	$ 523,849	$ 557,672
Net income	$ 73,834	$ 109,736
Earnings per share
Basic	$ 0.52	$ 0.78
Diluted	$ 0.51	$ 0.77
Weighted average ordinary shares outstanding (thousand)
Basic	142,738	140,919
Diluted	143,606	142,050

Details of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

^[1]

Cash and Cash Equivalents [Line Items]

Cash and deposits in bank

$ 59,751

$ 58,391

Time deposits

269,392

199,064

Bonds acquired under repurchase agreements

30,310

17,028

Total cash and cash equivalents

359,453

274,483

$ 180,519

$ 194,211

Restricted cash (Note 2)

22,070

46,694

Total cash ,cash equivalents, and restricted cash

$ 381,523

$ 321,177

$ 202,156

^[1]

$ 215,892

^[1]

$ 179,584

[1]	The restricted cash is only included in the amount of "as adjusted" item.

Short Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 6,941	$ 3,302

Short Term Investments - Additional Information (Detail) - Trading Securities [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Realized gains on sales of short-term investments, trading securities	$ 103,000	$ 2,000	$ 3,000
Unrealized holding loss on short-term investment	$ 0	$ 0	$ 0

Summary of Notes and Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable	$ 81,165	$ 75,946
Allowance for doubtful accounts	(598)	(723)	$ (775)	$ (1,167)
Allowance for sales returns and discounts	(1,432)	(1,624)	$ (1,555)	$ (1,427)
Notes and accounts receivable, net	$ 79,135	$ 73,599

Change in Allowances (Detail) - USD ($) $ in Thousands	12 Months Ended
Change in Allowances (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowances for doubtful accounts
Balance, beginning of year	$ 723	$ 775	$ 1,167
Reversals charged to expense, net	(125)	(12)	(392)
Write-offs		(40)
Balance, end of year	598	723	775
Allowances for sales returns and discounts
Balance, beginning of year	1,624	1,555	1,427
Additions charged to expense, net	3,093	3,285	1,753
Actual sales return and discount	(3,285)	(3,216)	(1,625)
Balance, end of year	$ 1,432	$ 1,624	$ 1,555

Components of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory [Line Items]
Finished goods	$ 41,365	$ 24,782
Work in process	25,090	31,185
Raw materials	27,731	15,920
Inventory, Net	$ 94,186	$ 71,887

Inventories - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory [Line Items]
Inventory written down	$ 698	$ 2,995	$ 2,525

Equity Investments with Carrying Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Cost-method Investments [Line Items]
Long-term investments		$ 120
Cashido Corp. (Cashido)
Schedule of Cost-method Investments [Line Items]
Long-term investments		$ 91
Equity Investments Percentage of Ownership	2.10%	2.10%
Vastview Technology, Corp. (Vastview)
Schedule of Cost-method Investments [Line Items]
Long-term investments		$ 29
Equity Investments Percentage of Ownership	2.90%	2.90%

Long-term Investment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended				36 Months Ended
	Feb. 28, 2007	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013	Dec. 31, 2009	Dec. 31, 2010
Cashido Corp. (Cashido)
Schedule of Cost-method Investments [Line Items]
Cost method investment impairments other than temporary		$ 91	$ 13
Vastview Technology, Corp. (Vastview)
Schedule of Cost-method Investments [Line Items]
Invested in common stock	$ 3,360
Cost method investment capital return				$ 46	$ 808
Recognized an impairment charges		$ 29				$ 2,462

Summary of Noncurrent Assets Held for Sale (Detail) $ in Thousands	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale	$ 3,363
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale	$ 3,363

Noncurrent Assets Held for Sale - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Gain (Loss) on disposition of other assets	$ 1,880

Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Land	$ 9,309	$ 9,309
Buildings	30,288	29,232
Machinery and equipment	21,665	18,122
Furniture and fixtures	7,746	6,760
Leasehold and buildings improvement	5,497	4,911
Software	24,864	22,745
Total	99,369	91,079
Accumulated Depreciation	48,436	43,668
Prepayment and construction in progress	437	481
Property, Plant and Equipment, Net	51,370	47,892	$ 50,469
Software
Property, Plant and Equipment [Line Items]
Accumulated Depreciation	19,874	19,130
Buildings
Property, Plant and Equipment [Line Items]
Accumulated Depreciation	3,472	2,708
Machinery and Equipment
Property, Plant and Equipment [Line Items]
Accumulated Depreciation	15,665	14,032
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Accumulated Depreciation	5,212	4,207
Leasehold and buildings improvement
Property, Plant and Equipment [Line Items]
Accumulated Depreciation	$ 4,213	$ 3,591

Property And Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating Leased Assets [Line Items]
Net carrying value of leased properties	$ 709	$ 728
Annual lease and rental income from operating lease	$ 42

Intangible Assets Acquired from Acquisition (Detail) - FCI, Centronix, BTL, Shannon and Bigtera - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Liabilities [Line Items]
Cost	$ 13,117	$ 8,381
Accumulated Impairment	0	0
Accumulated Amortization	(5,688)	(3,154)
Net Carrying Amount	$ 7,429	$ 5,227

Goodwill And Acquired Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			60 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011	Jul. 03, 2017	Jul. 01, 2015
Goodwill and Intangible Assets Disclosure [Line Items]
Intangible asset impairment losses		$ 0	$ 0	$ 0
Amortization of intangible assets		2,534	2,103	1,051
Goodwill impairment	$ 10,337	10,337	0	$ 0
Goodwill	$ 58,964	$ 58,964	$ 68,656
FCI, Centronix and BTL
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill acquired during period					$ 66,300
Shannon Systems
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill							$ 33,204
Bigtera
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill						$ 625

Schedule of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
Schedule of Goodwill (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Cost	$ 100,129	$ 99,504
Accumulated Impairment	(41,145)	(30,808)
Foreign Currency Adjustment	(20)	(40)
Net Carrying Amount	$ 58,964	$ 68,656

Short-Term Bank Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Bank loan	$ 25,000	$ 25,000
Secured Loans
Short-term Debt [Line Items]
Bank loan	$ 25,000	$ 25,000

Short-Term Bank Loans - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Bank	Dec. 31, 2015 USD ($)
Short-term Debt [Line Items]
Interest expense	$ 387	$ 105	$ 0
Number of banks \| Bank		2
Loans payable	25,000	$ 25,000
Pledged deposit	$ 0	$ 25,000
Expected repayment year of bank loan	2018
Minimum
Short-term Debt [Line Items]
Interest rate		0.953%
Maximum
Short-term Debt [Line Items]
Interest rate		1.51%

Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses and Other Current Liabilities [Line Items]
Wages and bonus	$ 29,629	$ 29,028
Dividends	32,451	21,382
Research and development payable	5,638	5,456
License fees and royalties	3,729	4,021
Professional fees	2,286	2,038
Equipment	1,844	492
Others	8,186	6,319
Accrued expenses and other current liabilities	$ 83,763	$ 68,736

Pension Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated benefit obligation	$ 3,210	$ 2,648	$ 2,098
Estimated amortization of net gain from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year	33
FCI
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
The contribution under defined benefit plans	0
Taiwan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions and Recognized Pension Costs under Labor Pension Act	$ 1,579	$ 1,272	$ 1,015
Contributions Based on Percentage Employee Salaries under Labor Standards Law	2.00%
The contribution under defined benefit plans	$ 69
Taiwan \| Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Contribution by an Employer to Employees Pension	6.00%

Changes in Benefits Obligation and Plan Assets and Reconciliation of Funded Status (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation
Projected benefit obligation at beginning of year	$ 4,242	$ 3,632	$ 3,320
Service cost	1,572	487	273
Interest cost	336	104	57
Actuarial loss (gain)	(665)	151	79
Benefits paid	(354)	(132)	(97)
Projected benefit obligation at end of year	5,131	4,242	3,632
Change in plan assets
Fair value of plan assets at beginning of year	3,902	2,800	2,556
Actual return on plan assets	81	33	33
Employer contributions	1,358	1,203	328
Benefits paid	(227)	(134)	(117)
Fair value of plan assets at end of year	5,114	3,902	2,800
Funded status recognized as an other asset (liabilities)	$ (17)	$ (340)	$ (832)

Amounts Recognized in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net loss	$ 678	$ 963	$ 852
Transition obligation			1
Total recognized in accumulated other comprehensive income	$ 678	$ 963	$ 853	$ 849

Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Periodic Benefit Cost:
Service cost	$ 1,572	$ 487	$ 273
Interest cost	336	104	57
Projected return on plan assets	(58)	(28)	(47)
Amortization of unrecognized net transition obligation and unrecognized net actuarial gain	37	11	27
Net periodic benefit cost	$ 1,887	$ 574	$ 310

Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Changes in Plan Assets and Benefit Obligation Recognized in Other Comprehensive Income (Loss):
Recognize the decrease in net gain (loss)	$ (285)	$ 111	$ 4
Amortization of net gain (loss)		(1)
Total recognized in other comprehensive loss (income)	$ (285)	$ 110	$ 4

Expected Benefit Payments (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Schedule Of Defined Benefit Plans Disclosures [Line Items]
2018	$ 188
2019	184
2020	407
2021	181
2022	182
2023 and thereafter	$ 2,057

Actuarial Assumptions to Determine Benefit Obligations (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Taiwan
Weighted-average assumptions used to determine benefit obligations:
Discount rate	1.63%	1.50%	1.75%
Rate of compensation increase	4.25%	4.25%	4.25%
Weighted-average assumptions used to determine net projected benefit cost:
Discount rate	1.63%	1.50%	1.75%
Expected long-term return on plan assets	1.75%	2.00%	2.00%
Rate of compensation increase	4.25%	4.25%	4.25%
Korea
Weighted-average assumptions used to determine benefit obligations:
Discount rate	4.10%	3.80%	3.90%
Rate of compensation increase	3.50%	3.50%	4.00%
Weighted-average assumptions used to determine net projected benefit cost:
Discount rate	4.10%	3.80%	3.90%
Expected long-term return on plan assets	1.10%	1.10%	1.20%
Rate of compensation increase	3.50%	3.50%	4.00%

Fair Values Of FCI's Pension Plan Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Defined Benefit Plans Disclosures [Line Items]
Fair value of pension plan assets	$ 5,114	$ 3,902	$ 2,800	$ 2,556
FCI
Schedule Of Defined Benefit Plans Disclosures [Line Items]
Fair value of pension plan assets	3,865	2,821
FCI \| Guaranteed Interest Contract \| Kyobo Life Insurance Co. Ltd.
Schedule Of Defined Benefit Plans Disclosures [Line Items]
Fair value of pension plan assets	1,599	1,284
FCI \| Guaranteed Interest Contract \| Shinhan Investment Co.
Schedule Of Defined Benefit Plans Disclosures [Line Items]
Fair value of pension plan assets	374
FCI \| Fixed Deposit \| Industrial Bank of Korea
Schedule Of Defined Benefit Plans Disclosures [Line Items]
Fair value of pension plan assets	$ 1,892	$ 1,537

Components of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components Of Income Tax Expense Benefit [Line Items]
Current	$ 23,465	$ 31,063	$ 17,338
Deferred	581	(3,373)	911
Income tax expense	$ 24,046	$ 27,690	$ 18,249

Income (loss) Before Income Taxes for Domestic and Foreign Entities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Income (loss) before income taxes, domestic	$ (27,902)	$ (20,663)	$ (12,037)
Income (loss) before income taxes, foreign	126,903	159,293	90,537
INCOME BEFORE INCOME TAX	$ 99,001	$ 138,630	$ 78,500

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Tax Credit Carryforward [Line Items]
Corporate income tax rate		17.00%
Change in valuation allowance		$ (1,764,000)	$ 1,792,000	$ 2,253,000
Rate of corporate surtax, unappropriated earnings		10.00%
Accumulated undistributed earnings from a foreign subsidiary		$ 325,000,000
Deferred tax liability on undistributed foreign earnings		0
Unrecognized tax benefit		15,056,000	10,286,000	5,639,000	$ 4,655,000
Total amount of interest expense and penalties		617,000	575,000	$ 363,000
Total amount of accrued interest and penalties		$ 3,421,000	$ 2,587,000
Cayman Islands Tax Information Authority [Member]
Tax Credit Carryforward [Line Items]
Corporate income tax rate		0.00%	0.00%	0.00%
Scenario, Plan
Tax Credit Carryforward [Line Items]
Corporate income tax rate	20.00%
Rate of corporate surtax, unappropriated earnings	5.00%
Deferred tax assets	$ 529,000
Foreign Tax Authority \| Internal Revenue Service (IRS) [Member]
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards for income tax purposes		$ 9,760,000
Federal net operating loss carryforwards expiration year		2037
Foreign Tax Authority \| Research And Development \| Internal Revenue Service (IRS) [Member]
Tax Credit Carryforward [Line Items]
Deferred tax assets tax credit carryforwards		$ 2,601,000
Tax credit carryforward expiration year for federal		2037
State and Local Jurisdiction [Member] \| Research And Development
Tax Credit Carryforward [Line Items]
Deferred tax assets tax credit carryforwards		$ 1,785,000
Tax credit carryforward expiration year for state		No expiration date
FCI \| Research And Development
Tax Credit Carryforward [Line Items]
Deferred tax assets tax credit carryforwards		$ 4,546,000
FCI \| Research And Development \| Minimum
Tax Credit Carryforward [Line Items]
Tax credit carryforward expiration year for federal		2018
FCI \| Research And Development \| Maximum
Tax Credit Carryforward [Line Items]
Tax credit carryforward expiration year for federal		2022

Reconciliation of Income Tax Expense on Pretax Income at Statutory Rate and Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation Of Income Taxes [Line Items]
Differences between Cayman and foreign statutory tax rates	$ 24,255	$ 34,415	$ 18,765
Tax-exempt income		(4,648)	(906)
Permanent differences	(4,249)	(7,792)	(1,065)
Temporary differences	(1,445)	(1,533)	(330)
Alternative minimum tax	4	594	4
Income tax (10%) on undistributed earnings	2,709	5,677	2,460
Net changes in income tax credit	166	(495)	(897)
Net changes in valuation allowance of deferred income tax assets	(2,401)	1,724	1,621
Net operating loss carryforwards	1,492	(1,689)	(2,052)
Liabilities related to unrealized tax benefits	3,455	2,385	672
Adjustment of prior years' taxes and others	60	(948)	(23)
Income tax expense	24,046	27,690	18,249
Cayman Islands Tax Information Authority [Member]
Reconciliation Of Income Taxes [Line Items]
Tax expense at statutory rate	$ 0	$ 0	$ 0

Deferred Income Tax Assets (liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Components of Deferred Tax Provision [Line Items]
Notes and accounts receivable	$ 44	$ 44
Stock-based compensation	771	1,146
Allowance for sales return	154	205
Inventory reserve	1,311	1,646
Foreign currency translation	(5)	2
Property and equipment	168	383
Investment tax credits	9,078	8,647
Net operating loss carryforwards	10,391	12,335
Others	562	411
Valuation allowance	(19,072)	(20,836)
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	$ 3,402	$ 3,983

Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Balance, beginning of year	$ 10,286	$ 5,639	$ 4,655
Increases in tax positions taken in current year	6,647	4,675	2,337
Decrease in tax position taken in prior year primarily related to the resolution of tax audit	(1,877)	(28)	(1,353)
Balance, end of year	$ 15,056	$ 10,286	$ 5,639

Summary of Major Jurisdictions and Tax Year Subject to Examination Tax Authorities (Detail)	12 Months Ended
	Dec. 31, 2017
China
Income Tax Examination [Line Items]
Years Subject to Income Tax Examination	2014 and onward
HONG KONG
Income Tax Examination [Line Items]
Years Subject to Income Tax Examination	2014 and onward
Taiwan
Income Tax Examination [Line Items]
Years Subject to Income Tax Examination	2012 and onward
Korea
Income Tax Examination [Line Items]
Years Subject to Income Tax Examination	2012 and onward
United States
Income Tax Examination [Line Items]
Years Subject to Income Tax Examination	2012 onward

Shareholders' Equity - Additional Information (Detail) - $ / shares			3 Months Ended								12 Months Ended
	Oct. 24, 2017	Oct. 24, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retained Earnings Adjustments [Line Items]
Dividend distribution allowance description											SMI Taiwan subsidiary may only distribute dividends after it has made allowances as determined under ROC GAAP at each year-end for a. Payment of taxes; b. Recovery of prior years' deficits, if any; c. 10% of remaining balance after deduction for a and b as legal reserve; d. Special reserve based on relevant laws or regulations or 10% of remaining balance for deduction from above a to c as special reserve when necessary.
Dividend declared	$ 0.3	$ 0.2	$ 0.075	$ 0.050	$ 0.050	$ 0.050	$ 0.0500	$ 0.0375	$ 0.0375	$ 0.0375	$ 0.30	$ 0.20	$ 0.2625
American Depositary Shares
Retained Earnings Adjustments [Line Items]
Dividend declared	$ 1.2	$ 0.8

Cash Dividends Declared Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended								12 Months Ended
	Oct. 24, 2017	Oct. 24, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Dividend Per Share	$ 0.3	$ 0.2	$ 0.075	$ 0.050	$ 0.050	$ 0.050	$ 0.0500	$ 0.0375	$ 0.0375	$ 0.0375	$ 0.30	$ 0.20	$ 0.2625
Amount			$ 10,737	$ 7,155	$ 7,148	$ 7,134	$ 7,065	$ 5,297	$ 5,290	$ 5,290	$ 32,174	$ 22,942

Equity Incentive Plan - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2010	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2009	Dec. 31, 2006	Jun. 03, 2015	Apr. 22, 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option exchange for new stock option granted	4,369,000
Stock options exercise price	$ 1.47
Eligible stock options exchanged for new stock options granted	3,785,000
Stock Option Granted		0	0	0
Stock Option Granted Intrinsic Value		$ 3,040,000	$ 580,000	$ 3,688,000
Total unrecognized compensation cost related to non-vested share-based compensation		0
Cash received from employee toward stock option exercise		380,000	93,000	494,000
Tax effect for stock-based compensation benefit (expense) for option and restricted stock units exercised		124,000	37,000	561,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted exercise price	$ 1.85
Employee Stock Options And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax effect for stock-based compensation benefit (expense) for option and restricted stock units exercised		$ 2,273,000	$ 1,702,000	$ 1,647,000
2005 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares authorized								10,000,000
Additional ordinary shares authorized					15,000,000	15,000,000
2005 Equity Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio of restricted stock unit to ordinary shares		One-for-one
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares authorized							20,000,000
The 2005 Plan and The 2015 Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to non-vested share-based compensation		$ 4,736,000
The 2005 Plan and The 2015 Plan \| Employee Stock Options And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares authorized				20,000,000

Summary of Stock Option and Restricted Stock Units Activity (Detail) - The 2005 Plan and The 2015 Plan - Employee Stock Options And Restricted Stock Units [Member] - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Available for grant at beginning date	18,751,000	19,862,000	1,687,000
Authorized			20,000,000
Restricted stock units granted	(1,391,000)	(1,446,000)	(2,000,000)
Option and restricted stock units forfeited	27,000	335,000	175,000
Available for grant at ending balance	17,387,000	18,751,000	19,862,000

Summary of Stock Option Activity and Related Information (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options Shares
Outstanding at beginning period	258	579	1,058
Options forfeited		(257)	(143)
Options exercised	(258)	(64)	(336)
Outstanding at ending period		258	579
Options vested and expected to vest after ending period		258	579
Weighted Average Exercise Price
Outstanding at beginning period	$ 1.47	$ 1.47	$ 1.47
Options forfeited		1.47	1.47
Options exercised	$ 1.47	1.47	1.47
Outstanding at ending period		1.47	1.47
Options vested and expected to vest after ending period		$ 1.47	$ 1.47
Weighted Average Remaining Contractual Life
Outstanding at ending period		3 months	11 months 1 day
Options vested and expected to vest after ending period		3 months	11 months 1 day

Summary of Status of Restricted Stock Units and Changes (Detail) - Restricted Stock Units - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Nonvested Stock Units
Nonvested at beginning period	1,767	2,125	2,160
Restricted stock units granted	1,391	1,446	2,000
Restricted stock units vested	(1,593)	(1,726)	(2,003)
Restricted stock units forfeited	(27)	(78)	(32)
Nonvested at ending period	1,538	1,767	2,125
Weighted Average Grant Date Fair Value
Nonvested at beginning period	$ 11.65	$ 6.65	$ 4.90
Restricted stock units granted	10.75	12.67	6.83
Restricted stock units vested	12.08	6.46	4.96
Restricted stock units forfeited	10.69	6.57	5.85
Nonvested at ending period	$ 10.36	$ 11.65	$ 6.65
Weighted Average Remaining Recognition Period (Years)
Nonvested at ending period	3 months 29 days	5 months 19 days	8 months 23 days

Table of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 15,494	$ 17,364	$ 10,418
Cost of Sales
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	293	400	261
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	9,255	10,529	6,565
Selling and Marketing Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	3,167	3,122	1,790
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 2,779	$ 3,313	$ 1,802

Commitments And Contingencies - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Apr. 17, 2009	Mar. 31, 2010	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 25, 2007
Commitments and Contingencies Disclosure [Line Items]
Restricted cash deposited			$ 22,070	$ 46,694
Operating lease rental expenses			3,131	2,595	$ 2,453
Minimum operating lease payment, 2018			3,711
Minimum operating lease payment, 2019			3,070
Minimum operating lease payment, 2020			1,541
Minimum operating lease payment, 2021			1,159
Minimum operating lease payment, 2022			65
Unpaid accounts receivable from distributor, filed for Chapter 11 bankruptcy protection			81,165	75,946
Adversary proceeding pending on litigation filled by AASI creditor liquidating trust	$ 854
Litigation settlement expenses		$ 220
All American
Commitments and Contingencies Disclosure [Line Items]
Unpaid accounts receivable from distributor, filed for Chapter 11 bankruptcy protection						$ 256
Distribution claim received as beneficiary			265
FCI
Commitments and Contingencies Disclosure [Line Items]
Restricted cash deposited			$ 468	$ 415

Segment Information - Additional Information (Detail)	12 Months Ended
Segment Information - Additional Information (Detail)	Dec. 31, 2017 Segment
Reportable segment	1

Revenue by Product Category (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
NET SALES	$ 523,404	$ 556,146	$ 361,297
Mobile Storage
Segment Reporting Information [Line Items]
NET SALES	480,735	510,687	302,910
Mobile Communications
Segment Reporting Information [Line Items]
NET SALES	37,447	39,322	50,896
Others
Segment Reporting Information [Line Items]
NET SALES	$ 5,222	$ 6,137	$ 7,491

Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	$ 523,404	$ 556,146	$ 361,297
Taiwan
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	72,768	75,926	71,387
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	40,344	59,390	39,558
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	18,797	17,070	19,636
Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	176,813	183,249	150,118
China
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	126,048	151,112	69,623
Others
Revenues from External Customers and Long-Lived Assets [Line Items]
NET SALES	$ 88,634	$ 69,399	$ 10,975

Major customers representing at least 10% of net sales (Detail) - Net sales - Customers accounted for 10% or more - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

SK Hynix

Revenue, Major Customer [Line Items]

Major customers, revenue

$ 150,762

$ 156,541

$ 108,645

Major customers, percentage of net sales

29.00%

28.00%

30.00%

Intel

Revenue, Major Customer [Line Items]

Major customers, revenue

$ 50,205

^[1]

Major customers, percentage of net sales

10.00%

^[1]

[1]	Less than 10%

Long-lived Assets (Property And Equipment, net) by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 51,370	$ 47,892	$ 50,469
Taiwan
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	36,369	34,011	32,014
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	242	237	274
Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	1,936	1,448	1,891
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	12,798	12,181	16,268
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 25	$ 15	$ 22

Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments - trading securities	$ 6,941	$ 3,302
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments - trading securities	755	695
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments - trading securities	$ 6,186	$ 2,607