Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jul. 31, 2016	Sep. 01, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jul. 31, 2016
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Trading Symbol	AMBA
Entity Registrant Name	AMBARELLA INC
Entity Central Index Key	0001280263
Current Fiscal Year End Date	--01-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		32,699,784

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Current assets:
Cash and cash equivalents	$ 276,507	$ 268,056
Marketable securities	50,520	39,837
Accounts receivable, net	33,588	39,408
Inventories	20,898	18,167
Restricted cash	8	7
Prepaid expenses and other current assets	4,180	4,170
Total current assets	385,701	369,645
Property and equipment, net	3,642	3,448
Deferred tax assets, non-current	5,743	4,626
Intangible assets, net	4,173	4,178
Goodwill	26,601	26,601
Other non-current assets	1,998	2,117
Total assets	427,858	410,615
Current liabilities:
Accounts payable	19,723	14,175
Accrued liabilities	23,123	23,778
Income taxes payable	0	787
Deferred revenue	5,464	10,077
Total current liabilities	48,310	48,817
Other long-term liabilities	2,793	12,342
Total liabilities	51,103	61,159
Commitments and contingencies (Note 13)	0	0
Shareholders' equity:
Preference shares, $0.00045 par value per share, 20,000,000 shares authorized and no shares issued and outstanding at July 31, 2016 and January 31, 2016, respectively	0	0
Ordinary shares, $0.00045 par value per share, 200,000,000 shares authorized at July 31, 2016 and January 31, 2016, respectively; 32,677,136 shares issued and outstanding at July 31, 2016; 32,333,359 shares issued and outstanding at January 31, 2016	15	15
Additional paid-in capital	181,690	176,306
Accumulated other comprehensive income (loss)	33	(7)
Retained earnings	195,017	173,142
Total shareholders’ equity	376,755	349,456
Total liabilities and shareholders' equity	$ 427,858	$ 410,615

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jul. 31, 2016	Jan. 31, 2016
Statement Of Financial Position [Abstract]
Preference shares, par value	$ 0.00045	$ 0.00045
Preference shares, shares authorized	20,000,000	20,000,000
Preference shares, shares issued	0	0
Preference shares, shares outstanding	0	0
Ordinary shares, par value	$ 0.00045	$ 0.00045
Ordinary shares, shares authorized	200,000,000	200,000,000
Ordinary shares, shares issued	32,677,136	32,333,359
Ordinary shares, shares outstanding	32,677,136	32,333,359

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Income Statement [Abstract]
Revenue	$ 65,142	$ 84,193	$ 122,299	$ 155,206
Cost of revenue	21,672	29,345	42,122	54,440
Gross profit	43,470	54,848	80,177	100,766
Operating expenses:
Research and development	23,643	20,840	48,109	37,423
Selling, general and administrative	10,565	9,087	21,458	18,097
Total operating expenses	34,208	29,927	69,567	55,520
Income from operations	9,262	24,921	10,610	45,246
Other income	171	127	198	154
Income before income taxes	9,433	25,048	10,808	45,400
Provision for income taxes	801	1,951	393	3,449
Net income	$ 8,632	$ 23,097	$ 10,415	$ 41,951
Net income per share attributable to ordinary shareholders:
Basic	$ 0.27	$ 0.73	$ 0.32	$ 1.34
Diluted	$ 0.25	$ 0.68	$ 0.31	$ 1.25
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	32,557,398	31,515,446	32,492,723	31,307,236
Diluted	34,175,466	33,904,222	34,063,103	33,688,239

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 8,632	$ 23,097	$ 10,415	$ 41,951
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on investments	13	(7)	40	(23)
Other comprehensive income (loss), net of tax	13	(7)	40	(23)
Comprehensive income	$ 8,645	$ 23,090	$ 10,455	$ 41,928

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Cash flows from operating activities:
Net income	$ 10,415	$ 41,951
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	842	755
Amortization/accretion of marketable securities	125	283
Loss on disposal of long-lived assets	10	8
Stock-based compensation	22,767	11,603
Excess income tax benefits associated with stock-based compensation	0	(263)
Other non-cash items, net	57	72
Changes in operating assets and liabilities, net of impact of acquisition:
Accounts receivable	5,820	(1,467)
Inventories	(2,731)	(5,979)
Prepaid expenses and other current assets	2	1,369
Deferred tax assets	1,054	(223)
Other assets	119	(26)
Accounts payable	5,548	(741)
Accrued liabilities	(543)	5,466
Income taxes payable	(787)	2,395
Deferred tax liabilities	(58)	(20)
Deferred revenue	(4,613)	2,034
Other long-term liabilities	26	23
Net cash provided by operating activities	38,053	57,240
Cash flows from investing activities:
Acquisition, net of cash acquired	0	(29,905)
Purchase of investments	(50,214)	(28,661)
Sales of investments	19,827	9,908
Maturities of investments	19,560	15,900
Purchase of property and equipment	(997)	(615)
Net cash used in investing activities	(11,824)	(33,373)
Cash flows from financing activities:
Stock repurchase	(20,183)	0
Proceeds from exercise of stock options and employee stock purchase plan	2,405	5,156
Excess income tax benefits associated with stock-based compensation	0	263
Net cash provided by (used in) financing activities	(17,778)	5,419
Net increase in cash and cash equivalents	8,451	29,286
Cash and cash equivalents at beginning of period	268,056	170,291
Cash and cash equivalents at end of period	276,507	199,577
Supplemental disclosure of cash flow information:
Cash paid for income taxes	637	551
Supplemental disclosure of noncash investing activities:
Increase in accrued liabilities related to non-monetary assets purchases	$ 86	$ 29

Organization and Summary of Significant Accounting Policies	6 Months Ended
	Jul. 31, 2016
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies Organization Ambarella, Inc. (the “Company”) was incorporated in the Cayman Islands on January 15, 2004. The Company is a developer of semiconductor processing solutions for video that enable high-definition video capture, sharing and display. The Company combines its processor design capabilities with its expertise in video and image processing, algorithms and software to provide a technology platform that is designed to be easily scalable across multiple applications and enable rapid and efficient product development. The Company’s system-on-a-chip, or SoC, designs fully integrate high-definition video processing, image processing, audio processing and system functions onto a single chip, delivering exceptional video and image quality, differentiated functionality and low power consumption. The Company sells its solutions to leading original design manufacturers, or ODMs, and original equipment manufacturers, or OEMs, globally. Basis of presentation The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in accordance with the instructions to Form 10-Q pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and notes normally provided in audited financial statements. The accounting policies are described in the “Notes to Consolidated Financial Statements” in the Annual Report on Form 10-K for the 2016 fiscal year filed with the SEC on March 25, 2016 (the “Form 10-K”) and updated, as necessary, in this Form 10-Q. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from audited financial statements, but does not include all disclosures required by generally accepted accounting principles in the United States (“U.S. GAAP”). In the opinion of management, all adjustments (consisting of normal recurring accruals and adjustments) considered necessary for a fair statement have been included. The results of operations for any interim period are not necessarily indicative of, nor comparable to, the results of operations for any other interim period or for a full fiscal year. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Form 10-K. Basis of Consolidation The Company’s fiscal year ends on January 31. The condensed consolidated financial statements of the Company and its subsidiaries have been prepared in conformity with U.S. GAAP. All intercompany transactions and balances have been eliminated upon consolidation. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expense during the reported periods. Actual results could differ from those estimates. On an ongoing basis, management evaluates its estimates and assumptions, including those related to (i) the collectibility of accounts receivable; (ii) write down of excess and obsolete inventories; (iii) intangible assets and goodwill; (iv) the estimated useful lives of long-lived assets; (v) impairment of long-lived assets and financial instruments; (vi) warranty obligations; (vii) the valuation of stock-based compensation awards and financial instruments; (viii) the probability of performance objectives achievement; (ix) the realization of tax assets and estimates of tax liabilities, including reserves for uncertain tax positions; and (x) the recognition and disclosure of contingent liabilities. These estimates and assumptions are based on historical experience and on various other factors which the Company believes to be reasonable under the circumstances. The Company may engage third-party valuation specialists to assist with estimates related to the valuation of financial instruments and assets associated with various contractual arrangements. Such estimates often require the selection of appropriate valuation methodologies and significant judgment. Actual results could differ from these estimates under different assumptions or circumstances. Concentration of Risk The Company’s products are manufactured, assembled and tested by third-party contractors located primarily in Asia. The Company does not have long-term agreements with these contractors. A significant disruption in the operations of one or more of these contractors would impact the production of the Company’s products which could have a material adverse effect on its business, financial condition and results of operations. A substantial portion of the Company’s revenue is derived from sales through its logistics provider, Wintech Microelectronics Co., Ltd., or Wintech, which serves as its non-exclusive sales representative in Asia other than Japan, and through one large direct ODM customer, Chicony Electronics Co., Ltd., or Chicony. Termination of the relationships with these two customers could result in a temporary or permanent loss of revenue and termination of the relationship with Wintech could result in an obligation to repurchase unsold product. Furthermore, any credit issues from these two customers could impair their abilities to make timely payment to the Company. See Note 14 for additional information regarding concentration with these two customers. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, marketable securities and accounts receivable. The Company maintains its cash primarily in checking and money market accounts with reputable financial institutions. Cash deposits held with these financial institutions may exceed the amount of insurance provided on such deposits. The Company has not experienced any material losses on deposits of its cash. The cash equivalents and marketable securities consist primarily of money market funds, asset-backed securities, commercial paper, U.S. government securities, agency bonds and debt securities of corporations which management assesses to be highly liquid, in order to limit the exposure of each investment. The Company does not hold or issue financial instruments for trading purposes. The Company performs ongoing credit evaluations of each of its customers and adjusts credit limits based upon payment history and the customer’s credit worthiness. The Company regularly monitors collections and payments from its customers. Cash Equivalents and Marketable Securities The Company considers all highly liquid investments with original maturities of less than three months at the time of purchase to be cash equivalents. Investments that are highly liquid with original maturities at the time of purchase greater than three months are considered as marketable securities. The Company classifies these investments as “available-for-sale” securities carried at fair value, based on quoted market prices of similar assets, with the unrealized gains or losses reported, net of tax, as a separate component of shareholders’ equity and included in accumulated other comprehensive income (loss) in the condensed consolidated balance sheets. The amortization of security premiums and accretion of discounts and the realized gains and losses are both recorded in other income (loss), net in the condensed consolidated statements of operations. The Company reviews its investments for possible other-than-temporary impairments on a regular basis. If any loss on investment is believed to be other-than-temporary, a charge will be recorded and a new cost basis in the investment will be established. In evaluating whether a loss on a security is other-than-temporary, the Company considers the following factors: 1) general market conditions, 2) the duration and extent to which the fair value is less than cost, 3) the Company’s intent and ability to hold the investment. For securities in an unrealized loss position which is deemed to be other-than-temporary, the difference between the security’s then-current amortized cost basis and fair value is separated into (i) the amount of the impairment related to the credit loss (i.e., the credit loss component) and (ii) the amount of the impairment related to all other factors (i.e., the non-credit loss component). The credit loss component is recognized in earnings. The non-credit loss component is recognized in accumulated other comprehensive income (loss). Due to the relative short term nature of the investments, there have been no other-than-temporary impairments recorded to date. Inventories The Company records inventories at the lower of cost or market. The cost includes materials and other production costs and is computed using standard cost on a first-in, first-out basis. Inventory reserves are recorded for estimated obsolescence or unmarketable inventories based on forecast of future demand and market conditions. If actual market conditions are less favorable than projected, or if future demand for the Company’s products decrease, additional inventory write-downs may be required. Once inventory is written down, a new accounting cost basis is established and, accordingly, any associated reserve is not reversed until the inventory is sold or scrapped. There were no material inventory losses recognized for the three and six months ended July 31, 2016 and 2015, respectively. Business Combinations and Intangible Assets The Company allocates the fair value of purchase price to the assets acquired and liabilities assumed based on their estimated fair values. The excess of the fair value of purchase price over the fair values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair values of assets acquired and liabilities assumed, especially with respect to intangible assets, management makes significant estimates and assumptions. Critical estimates in valuing certain intangible assets include, but are not limited to, replacement cost. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Goodwill and In-Process Research and Development Goodwill and in-process research and development (“IPR&D”) are required to be tested for impairment at least annually or sooner whenever events or changes in circumstances indicate that the assets may be impaired. The Company has a single reporting unit for goodwill impairment test purposes based on its business and reporting structure. The Company does not amortize goodwill. Acquired IPR&D is capitalized at fair value as an intangible asset and amortization commences upon completion of the underlying projects. When a project underlying reported IPR&D is completed, the corresponding amount of IPR&D is reclassified as an amortizable purchased intangible asset and is amortized over its estimated useful life. Revenue Recognition The Company generates revenue from the sales of its SoCs to OEMs or ODMs, either directly or through logistics providers. Revenue from sales directly to OEMs and ODMs is recognized upon shipment provided persuasive evidence of an arrangement exists, legal title to the products and risk of ownership have transferred, the fee is fixed or determinable, and collection of the resulting receivable is reasonably assured. The Company provides its logistics providers with the rights to return excess levels of inventory and to future price adjustments. Given the inability to reasonably estimate these price changes and returns, revenue and costs related to shipments to logistics providers are deferred until the Company has received notification from its logistics providers that they have sold the Company’s products. Information reported by the Company’s logistics providers includes product resale price, quantity and end customer shipment information as well as remaining inventory on hand. At the time of shipment to a logistics provider, the Company records a trade receivable as there is a legally enforceable right to receive payment, reduces inventory for the value of goods shipped as legal title has passed to the logistics provider and defers the related margin as deferred revenue in the condensed consolidated balance sheets. Any price adjustments are recorded as a change to deferred revenue at the time the adjustments are agreed upon. Arrangements with certain OEM customers provide for pricing that is dependent upon the end products into which the Company’s SoCs are used. These arrangements may also entitle the Company to a share of the product margin ultimately realized by the OEM. The minimum guaranteed amount of revenue related to the sale of products subject to these arrangements is recognized when all other elements of revenue recognition are met. Any amounts at the date of shipment invoiced in excess of the minimum guaranteed contract price are deferred until the additional amounts the Company is entitled to are fixed or determinable. Additional amounts earned by the Company resulting from margin sharing arrangements and determination of the end products into which the products are ultimately incorporated are recognized when end customer sales volume is reported to the Company. The Company also enters into engineering service agreements with certain customers. These agreements may include multiple deliverables, such as software development services, licensing of intellectual property and post-contract customer support, or PCS. The Company does not sell separately any of these components and does not have Vendor Specific Objective Evidence, or VSOE, for the deliverables. Accordingly, revenues from these agreements are deferred for any amounts billed until delivery of all the elements. If the agreements include PCS, the revenues are recognized ratably over the estimated supporting periods. The revenue from engineering service agreements was not material for the three and six months ended July 31, 2016 and 2015, respectively. Cost of Revenue Cost of revenue includes cost of materials, cost associated with packaging and assembly, testing and shipping, cost of personnel, stock-based compensation, logistics and quality assurance, warranty cost, royalty expense, write-downs of inventories and allocation of overhead. Income Taxes The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements or tax returns. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized. The Company applies authoritative guidance for the accounting for uncertainty in income taxes. The guidance requires that tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. Upon estimating the Company’s tax positions and tax benefits, the Company considered and evaluated numerous factors, which may require periodic adjustments and which may not reflect the final tax liabilities. The Company adjusts its financial statements to reflect only those tax positions that are more likely than not to be sustained under examination. As part of the process of preparing condensed consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differing treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets, which are included in the condensed consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the condensed consolidated statements of operations become deductible expenses under applicable income tax laws, or loss or credit carryforwards are utilized. In assessing whether deferred tax assets may be realized, management considers whether it is more likely than not that some portion or all of deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income. The Company makes estimates and judgments about its future taxable income based on assumptions that are consistent with its plans and estimates. Should the actual amounts differ from estimates, the amount of valuation allowance could be materially impacted. Any adjustment to the deferred tax asset valuation allowance would be recorded in the condensed consolidated income statement for the periods in which the adjustment is determined to be required. Net Income Per Ordinary Share Basic earnings per share is computed by dividing net income available to ordinary shareholders by the weighted-average number of ordinary shares outstanding during the period. Diluted earnings per share is computed by dividing net income available to ordinary shareholders by the weighted-average number of ordinary shares outstanding during the period increased to include the number of additional ordinary shares that would have been outstanding if the potentially dilutive securities had been issued. Potentially dilutive securities include outstanding stock options, shares to be purchased under the Company’s employee stock purchase plan, unvested restricted stock and restricted stock units. The dilutive effect of potentially dilutive securities is reflected in diluted earnings per share by application of the treasury stock method. Comprehensive Income (Loss) Comprehensive income (loss) includes unrealized gains or losses from available-for-sale securities that are excluded from net income. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). The new guidance clarifies the principles and develops a common revenue recognition guidance for U.S. GAAP and International Financial Reporting Standards (the “IFRS”). Under the new guidance, an entity is required to recognize an amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The original effective date of the ASU would have required the public companies to adopt the standard for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. In July 2015, the FASB voted to amend the ASU by approving a one-year deferral of the effective date as well as providing the option to early adopt the standard on the original effective date. The deferral results in this new revenue standard being effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606) – Principal versus Agent Considerations (“ASU 2016-08”), which clarifies the implementation guidance for principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606) – Identifying Performance Obligations and Licensing (“ASU 2016-10”), which amends the guidance in ASU 2014-09 related to identifying performance obligations and accounting for licenses of intellectual property. Accordingly, the Company must adopt ASU 2016-08 and ASU 2016-10 with ASU 2014-09 in its first quarter of fiscal year 2019. The new revenue guidance may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact of adoption on its financial position, results of operations and disclosures. In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. In connection with each annual and interim period, management is required to assess whether there is substantial doubt about an entity’s ability to continue as a going concern within one year after the issuance date, and to provide related footnote disclosures in certain circumstances. The new guidance is effective for annual periods ending after December 15, 2016, and interim periods within annual periods beginning after December 15, 2016. Early adoption is permitted. This ASU is not expected to have an impact on the Company’s financial statements or disclosures. In July 2015, the FASB issued ASU No. 2015-11, Simplifying the Measurement of Inventory. The new guidance changes the measurement principle for inventory from the lower of cost or market to 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. It applies to entities that measure inventory using a method other than last-in, first-out (“LIFO”) and the retail inventory method (“RIM”). The new guidance will be effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years and should be applied prospectively. Early adoption is permitted as of the beginning of an interim or annual reporting period. The Company is currently evaluating the impact of adoption on its financial position, results of operations and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This standard requires entities that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The standard is effective for fiscal years and the interim periods within those fiscal years beginning after December 15, 2018. The guidance is required to be applied by the modified retrospective transition approach. Early adoption is permitted. The Company is currently assessing the impact of the adoption of this new guidance on its financial position, results of operations and disclosures. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, to simplify and improve the accounting for employee share-based awards. The new standard amends the accounting for employee share-based payment transactions to require recognition of the tax effects resulting from the settlement of stock-based awards as income tax benefit or expense in the income statement in the reporting period in which they occur. In addition, the tax-related cash flows resulting from share-based payments will be classified as cash flows from operating activities and cash payments made to the taxing authorities on the employees’ behalf for withheld shares will be classified as financing activities on the statement of cash flows. The new guidance also provides an accounting policy election to account for forfeitures as they occur. The new guidance is effective for public entities for annual reporting periods beginning after December 15, 2016, and interim periods within that reporting period. Early adoption is permitted with any adjustments reflected as of the beginning of the fiscal year of adoption. The Company elected to early adopt this new guidance in the first quarter of its fiscal year 2017. As a result of this adoption, the Company recorded an increase to retained earnings of $11.7 million to recognize U.S. net operating loss carryforwards attributable to tax benefits from excess stock-based compensation that had not been previously recognized and recorded a decrease to retained earnings of $0.2 million resulting from the election of accounting policy to account for forfeitures as they occur as of February 1, 2016. The Company also elected to apply the presentation for cash flows related to excess tax benefits prospectively. The presentation requirements for cash flows related to employee taxes paid for withheld shares has no impact on the Company’s condensed consolidated statements of cash flows. On February 1, 2016, the cumulative effect adjustment of these changes recognized in the beginning of retained earnings was approximately $11.5 million. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326), to introduce a new impairment model for recognizing credit losses on financial instruments based on an estimated of current expected credit losses (ECL). Under the new model, available-for-sale (AFS) debt securities are required to estimate ECL only when the fair value is below the amortized cost of the asset and is no longer based on an impairment being “other-than-temporary”. The new model also requires the impairment calculation on an individual security level and requires an entity use present value of cash flows when estimating the ECL. The credit-related losses are required to be recognized through earnings and non-credit related losses are reported in other comprehensive income. The ASU will be effective for public entities in fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. The new guidance will require modified retrospective application to all outstanding instruments, with a cumulative effect adjustment recorded to opening retained earnings as of the beginning of the first period in which the guidance becomes effective. The Company does not believe the adoption of this new guidance will have material impact on its consolidated financial statements.

Financial Instruments and Fair Value

6 Months Ended

Jul. 31, 2016

Investments All Other Investments [Abstract]

Financial Instruments and Fair Value

2. Financial Instruments and Fair Value

The Company invested a portion of its cash in debt securities that are denominated in U.S. dollars. The investment portfolio consists of money market funds, demand deposit, asset-backed securities, commercial paper, U.S. government securities, agency bonds and debt securities of corporations. All of the investments are classified as available-for-sale securities and reported at fair value in the condensed consolidated balance sheets as follows:

	As of July 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market funds	$	103	$	—	$	—		$	103
Demand deposit		10,000		—		—			10,000
Commercial paper		7,479		—		—			7,479
Corporate bonds		19,342		17		(2	)		19,357
Asset-backed securities		8,446		6		—			8,452
U.S. government securities		13,197		11		—			13,208
Agency bonds		2,023		1		—			2,024
Total cash equivalents and marketable securities	$	60,590	$	35	$	(2	)	$	60,623

	As of January 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market funds	$	530	$	—	$	—		$	530
Commercial paper		2,598		—		—			2,598
Corporate bonds		21,342		7		(9	)		21,340
Asset-backed securities		4,586		—		(1	)		4,585
U.S. government securities		9,274		4		(6	)		9,272
Agency bonds		2,044		—		(2	)		2,042
Total cash equivalents and marketable securities	$	40,374	$	11	$	(18	)	$	40,367

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Included in cash equivalents	$	10,103	$	530
Included in marketable securities		50,520		39,837
Total cash equivalents and marketable securities	$	60,623	$	40,367

The contractual maturities of the investments at July 31, 2016 and January 31, 2016 were as follows:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Due within one year	$	52,856	$	33,449
Due within one to two years		7,767		6,918
Total cash equivalents and marketable securities	$	60,623	$	40,367

The unrealized losses on the available-for-sale securities were caused by fluctuations in market value and interest rates as a result of the economic environment. As the decline in market value was attributable to changes in market conditions and not credit quality, and because the Company neither intended to sell nor was it more likely than not that it would be required to sell these investments prior to a recovery of par value, the Company did not consider these investments to be other-than temporarily impaired as of July 31, 2016 and January 31, 2016, respectively.

The following fair value hierarchy is applied for disclosure of the inputs used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows:

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

Level 2—Inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the assets or liabilities, either directly or indirectly through market corroboration, for substantially the full term of the financial instruments.

Level 3—Unobservable inputs based on the Company’s own assumptions used to measure assets and liabilities at fair value. The inputs require significant management judgment or estimation.

The Company measures the fair value of money market funds and demand deposit using quoted prices in active markets for identical assets and classifies them within Level 1. The fair value of the Company’s investments in other debt securities are obtained based on quoted prices for similar assets in active markets, or model driven valuations using significant inputs derived from or corroborated by observable market data and are classified within Level 2.

The following table presents the fair value of the financial instruments measured on a recurring basis as of July 31, 2016 and January 31, 2016:

	As of July 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	103	$	103	$	—	$	—
Demand deposit		10,000		10,000		—
Commercial paper		7,479		—		7,479		—
Corporate bonds		19,357		—		19,357		—
Asset-backed securities		8,452		—		8,452		—
U.S. government securities		13,208		—		13,208		—
Agency bonds		2,024		—		2,024		—
Total cash equivalents and marketable securities	$	60,623	$	10,103	$	50,520	$	—

	As of January 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	530	$	530	$	—	$	—
Commercial paper		2,598		—		2,598		—
Corporate bonds		21,340		—		21,340		—
Asset-backed securities		4,585		—		4,585		—
U.S. government securities		9,272		—		9,272		—
Agency bonds		2,042		—		2,042		—
Total cash equivalents and marketable securities	$	40,367	$	530	$	39,837	$	—

Inventories

6 Months Ended

Jul. 31, 2016

Inventory Disclosure [Abstract]

Inventories

3. Inventories

Inventory at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Work-in-progress	$	11,944	$	9,474
Finished goods		8,954		8,693
Total	$	20,898	$	18,167

Property and Equipment, Net

6 Months Ended

Jul. 31, 2016

Property Plant And Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

Depreciation expense was approximately $0.3 million and $0.4 million for the three months ended July 31, 2016 and 2015, respectively. Depreciation expense was approximately $0.8 million for the six months ended July 31, 2016 and 2015, respectively. Property and equipment at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016			January 31, 2016
	(in thousands)
Computer equipment and software	$	6,700		$	6,421
Machinery and equipment		3,004			2,706
Furniture and fixtures		794			492
Leasehold improvements		1,550			1,429
Construction in progress		195			253
		12,243			11,301
Less: accumulated depreciation and amortization		(8,601	)		(7,853	)
Total property and equipment, net	$	3,642		$	3,448

Goodwill and Intangible Assets	6 Months Ended
Goodwill and Intangible Assets	Jul. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	5. Goodwill and Intangible Assets On June 25, 2015, the Company completed the acquisition of VisLab S.r.l., a privately held Italian company that develops computer vision and intelligent control systems for automotive and other commercial applications, including advanced driver assistance systems and several generations of autonomous vehicle driving systems, for $30.0 million in cash. As a result, there was $25.3 million attributed to goodwill, $4.1 million attributed to intangible assets and $0.6 million attributed to net assets acquired. A deferred tax liability of $1.3 million related to the intangible assets was recorded to account for the difference between financial reporting and tax basis at the acquisition date, with an addition to goodwill. The Company does not amortize goodwill. The intangible assets primarily consist of IPR&D. Acquired IPR&D is capitalized at fair value as an intangible asset and amortization commences upon completion of the underlying projects. When a project underlying reported IPR&D is completed, the corresponding amount of IPR&D is reclassified as an amortizable purchased intangible asset and is amortized over its estimated useful life. As of July 31, 2016, there was no IPR&D amortized. There were no goodwill or intangible asset impairments for the three and six months ended July 31, 2016 and 2015, respectively. Pro forma results of operations for this acquisition have not been presented because they are not material to the consolidated results of operations.

- 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

Accrued Liabilities

6 Months Ended

Jul. 31, 2016

Payables And Accruals [Abstract]

Accrued Liabilities

6. Accrued Liabilities

Accrued liabilities at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Accrued employee compensation	$	11,806	$	14,512
Accrued warranty		200		234
Accrued rebates		1,191		824
Accrued product development costs		7,544		6,339
Other accrued liabilities		2,382		1,869
Total accrued liabilities	$	23,123	$	23,778

Deferred Revenue and Deferred Cost

6 Months Ended

Jul. 31, 2016

Deferred Revenue Disclosure [Abstract]

Deferred Revenue and Deferred Cost

7. Deferred Revenue and Deferred Cost

Deferred revenue and related cost at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016			January 31, 2016
	(in thousands)
Deferred revenue on product shipments	$	6,048		$	12,201
Deferred revenue from licenses & services		1,957			1,653
Deferred cost of revenue on product shipments		(2,541	)		(3,777	)
Total deferred revenue, net	$	5,464		$	10,077

- Definition

The entire disclosure for deferred revenues at the end of the reporting period, and description and amounts of significant changes that occurred during the reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References + Details

Other Long-Term Liabilities

6 Months Ended

Jul. 31, 2016

Other Liabilities Disclosure [Abstract]

Other Long-Term Liabilities

8. Other Long-Term Liabilities

Other long-term liabilities at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Unrecognized tax benefits, including interest	$	1,427	$	10,917
Deferred tax liabilities, non-current		1,364		1,423
Other long-term liabilities		2		2
Total other long-term liabilities	$	2,793	$	12,342

On February 1, 2016, upon the adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, the Company recognized approximately $11.7 million of tax-effected previously unrecognized excess stock-based compensation deductions. As a result of recognizing these deductions, the Company reduced its unrecognized tax benefits by $9.5 million pursuant to accounting guidance, which provides that an unrecognized tax benefit shall be presented as a reduction to a deferred tax benefit to the extent such deferred tax benefit is available.

Capital Stock

6 Months Ended

Jul. 31, 2016

Equity [Abstract]

Capital Stock

9. Capital Stock

Preference shares

After completion of the Company’s initial public offering, or IPO, a total of 20,000,000 preference shares, with a $0.00045 par value per share, were authorized. There were no preference shares issued and outstanding as of July 31, 2016 and January 31, 2016, respectively.

Ordinary shares

As of July 31, 2016 and January 31, 2016, a total of 200,000,000 ordinary shares were authorized.

On February 1, 2016, the Company added 1,455,001 ordinary shares to the ordinary shares reserved for issuance, pursuant to an “evergreen” provision contained in the 2012 Equity Incentive Plan, or EIP. Pursuant to such provision, on February 1st of each fiscal year, the number of ordinary shares reserved for issuance under the EIP is automatically increased by a number equal to the lesser of (i) 3,500,000 ordinary shares, (ii) four and one half percent (4.5%) of the aggregate number of ordinary shares outstanding on January 31st of the preceding fiscal year, or (iii) a lesser number of shares that may be determined by the Company’s Board of Directors.

On February 1, 2016, the Company added 404,166 ordinary shares to the ordinary shares reserved for issuance, pursuant to an “evergreen” provision contained in the Amended and Restated 2012 Employee Stock Purchase Plan, or ESPP. Pursuant to such provision, on February 1st of each fiscal year, the number of ordinary shares reserved for issuance under the ESPP is automatically increased by a number equal to the lesser of (i) 1,500,000 ordinary shares, (ii) one and one quarter percent (1.25%) of the aggregate number of ordinary shares outstanding on such date, or (iii) an amount determined by the Company’s Board of Directors or a duly authorized committee of the Board of Directors.

As of July 31, 2016 and January 31, 2016, the following ordinary shares were reserved for future issuance under the EIP and ESPP:

	As of
	July 31, 2016		January 31, 2016
Shares reserved for options, restricted stock and restricted stock units		5,791,467		5,027,475
Shares reserved for employee stock purchase plan		1,320,582		974,273

Shares repurchased

On May 31, 2016, the Company’s Board of Directors authorized the repurchase of up to $75.0 million of the Company’s ordinary shares over a six-month period. Repurchases may be made from time-to-time through open market purchases or through privately negotiated transactions subject to market conditions, applicable legal requirements and other relevant factors. The repurchase program does not obligate the Company to acquire any particular amount of ordinary shares, and it may be suspended at any time at the Company’s discretion. The repurchase program will be funded using the Company’s working capital and any repurchased shares will be recorded as authorized but unissued shares and available for general corporate purposes. As of July 31, 2016, a total of 405,089 shares were repurchased for approximately $20.2 million in cash and recorded as a reduction to equity.

Stock-based Compensation

6 Months Ended

Jul. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

10. Stock-based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands)
Stock-based compensation:
Cost of revenue	$	246	$	127	$	491	$	251
Research and development		6,873		3,671		13,592		6,765
Selling, general and administrative		4,347		2,323		8,684		4,587
Total stock-based compensation	$	11,466	$	6,121	$	22,767	$	11,603

As of July 31, 2016, total unrecognized compensation cost related to unvested stock options was $10.0 million and is expected to be recognized over a weighted-average period of 2.16 years. Total unrecognized compensation cost related to unvested restricted stock units was $81.2 million and is expected to be recognized over a weighted-average period of 2.82 years. Total unrecognized compensation cost related to unvested restricted stock awards was $9.5 million and is expected to be recognized over a weighted-average period of 2.06 years.

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Three Months Ended July 31,						Six Months Ended July 31,
	2016			2015			2016			2015
Stock Options:
Volatility		38	%		57	%		38	%		59	%
Risk-free interest rate		1.39	%		1.85	%		1.55	%		1.76	%
Expected term (years)	6.08				6.08		5.96				6.08
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		—			—			67	%		63	%
Risk-free interest rate		—			—			0.52	%		0.15	%
Expected term (years)		—			—			0.5			0.5
Dividend yield		—			—			0	%		0	%

The following table summarizes stock option activities for the six months ended July 31, 2016:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value of		Remaining		Aggregate
				Weighted-		Average		options		Contractual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2016		1,853,390		$	19.36
Granted		78,700			41.93	$	16.38
Exercised		(65,836	)		10.96			$	2,176
Forfeited		(8,625	)		52.43
Expired		(7,721	)		14.12
Outstanding at July 31, 2016		1,849,908			20.48					5.59		$	71,725
Exercisable at July 31, 2016		1,430,350		$	13.00						4.75	$	65,004

The intrinsic value of options outstanding, exercisable, vested and expected-to-vest options are calculated based on the difference between the fair market value of the Company’s ordinary shares on the reporting date and the exercise price. The closing price of the Company’s ordinary shares was $57.98 on July 31, 2016, as reported by The NASDAQ Global Market. The intrinsic value of exercised options is calculated based on the difference between the fair market value of the Company’s ordinary shares on the exercise date and the exercise price.

The following table summarizes restricted stock activities for the periods indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2016		2,495,488		$	47.04
Granted		25,504			43.64
Vested		(464,699	)		35.56
Forfeited		(11,703	)		46.10
Unvested at July 31, 2016		2,044,590		$	48.03

As of July 31, 2016, the aggregate intrinsic value of unvested restricted stock was $118.5 million.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Net Income Per Ordinary Share

6 Months Ended

Jul. 31, 2016

Earnings Per Share [Abstract]

Net Income Per Ordinary Share

11. Net Income Per Ordinary Share

The following table sets forth the computation of basic and diluted net income per ordinary share for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands, except share and per share data)
Numerator:
Net income	$	8,632	$	23,097	$	10,415	$	41,951
Less: amount allocable to unvested early exercised options		—		—		—		—
Net income allocable to ordinary shareholders - basic	$	8,632	$	23,097	$	10,415	$	41,951
Undistributed earnings reallocated to ordinary shareholders		—		—		—		—
Net income allocable to ordinary shareholders - diluted	$	8,632	$	23,097	$	10,415	$	41,951
Denominator:
Weighted-average ordinary shares outstanding		32,557,398		31,515,446		32,492,723		31,307,292
Less: weighted-average unvested early exercised options subject to repurchase		—		—		—		(56	)
Weighted-average ordinary shares - basic		32,557,398		31,515,446		32,492,723		31,307,236
Effect of potentially dilutive securities:
Employee stock options		1,074,331		1,351,924		1,062,310		1,374,810
Restricted stock and restricted stock units		530,279		1,028,899		498,128		995,092
Employee stock purchase plan		13,458		7,953		9,942		11,101
Weighted-average ordinary shares - diluted		34,175,466		33,904,222		34,063,103		33,688,239
Net income per ordinary share:
Basic	$	0.27	$	0.73	$	0.32	$	1.34
Diluted	$	0.25	$	0.68	$	0.31	$	1.25

The following weighted-average potentially dilutive securities were excluded from the computation of diluted net income per ordinary share as their effect would have been antidilutive:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
Options to purchase ordinary shares		471,534		13,081		476,116		42,257
Restricted stock and restricted stock units		893,341		93,002		1,047,630		46,501
Employee stock purchase plan		—		—		17,191		6,714
Early exercised options subject to repurchase		—		—		—		56
		1,364,875		106,083		1,540,937		95,528

Income Taxes

6 Months Ended

Jul. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

The following table provides details of income taxes for the periods indicated:

	Three Months Ended July 31,						Six Months Ended July 31,
	2016			2015			2016			2015
	(in thousands)
Income before income taxes	$	9,433		$	25,048		$	10,808		$	45,400
Provision for income taxes		801			1,951			393			3,449
Effective tax rate	8.5		%		7.8	%	3.6		%		7.6	%

The increase in the effective tax rate for the three months ended July 31, 2016 compared to the same period of last fiscal year was primarily due to an increase in non-deductible stock-based compensation and the change in the mix of earnings in various geographic jurisdictions between the two periods. The decrease in the effective tax rate for the six months ended July 31, 2016 was primarily due to an approximately $34.6 million decrease in income before income tax as compared to the same period of last fiscal year, and a $1.1 million increase in discrete tax benefits recorded for the six months ended July 31, 2016. The increase in discrete tax benefits recorded was largely related to a change in the U.S. federal tax rate at which the Company’s deferred taxes are expected to reverse and tax benefits from excess stock-based compensation deductions following the Company’s early adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, in the first quarter of fiscal year 2017.

The Company files federal and state income tax returns in the United States and in various foreign jurisdictions. The tax years 2013 to 2016 remain open to examination by U.S. federal tax authorities. The tax years 2004 to 2016 remain open to examination by U.S. state tax authorities. The tax years 2010 to 2016 remain open to examination by material foreign tax authorities.

The Company is subject to ongoing examinations of its tax returns by the Internal Revenue Service and other tax authorities in various jurisdictions. The Company regularly assesses the likelihood of adverse outcomes resulting from these examinations to determine the adequacy of its provision for income taxes. These assessments can require considerable estimates and judgments. As of July 31, 2016, the gross amount of unrecognized tax benefits was approximately $33.6 million. If the estimates of income tax liabilities prove to be less than the ultimate assessment, then a further charge to expense could be required. If events occur and the payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities could result in tax benefits being recognized in the period in which the Company determines the liabilities are no longer necessary. The Company does not anticipate significant changes to its uncertain tax positions during the next twelve months.

Commitments and Contingencies

6 Months Ended

Jul. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

13. Commitments and Contingencies

The Company leases its principal facilities and time-based software licenses under operating lease agreements. Net operating lease expenses for the three months ended July 31, 2016 and 2015 were approximately $1.9 million and $1.7 million, respectively. Net operating lease expenses for the six months ended July 31, 2016 and 2015 were approximately $3.6 million, respectively. Future annual minimum payments under these operating leases with initial lease terms in excess of one year are as follows:

	As of
	July 31, 2016
Fiscal Year	(in thousands)
2017	$	3,533
2018		2,662
2019		1,955
2020		1,531
2021		515
Total future annual minimum lease payments	$	10,196

Contract Manufacturer Commitments

The Company’s components and products are procured and built by independent contract manufacturers based on sales forecasts. These forecasts include estimates of future demand, historical trends, analysis of sales and marketing activities, and adjustment of overall market conditions. The Company regularly issues purchase orders to independent contract manufacturers which are cancelable only upon the agreement between the Company and the third-party manufacturers. As of July 31, 2016 and January 31, 2016, total manufacturing purchase commitments were approximately $31.0 million and $19.7 million, respectively, as a result of seasonal fluctuations.

Indemnification

The Company, from time to time, in the normal course of business, indemnifies certain vendors with whom it enters into contractual relationships. The Company has agreed to hold the other party harmless against third-party claims in connection with the Company’s future products. The Company also indemnifies certain customers against third-party claims related to certain intellectual property matters. It is not possible to determine the maximum potential amount of liability under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances that are likely to be involved in each particular claim. The Company has not made payments under these obligations and no liabilities have been recorded for these obligations on the condensed consolidated balance sheets as of July 31, 2016 and January 31, 2016, respectively.

Segment Reporting

6 Months Ended

Jul. 31, 2016

Segment Reporting [Abstract]

Segment Reporting

14. Segment Reporting

The Company operates in one reportable segment related to the development and sales of low-power, high-definition video products. The Chief Executive Officer of the Company has been identified as the Chief Operating Decision Maker (the “CODM”) and manages the Company’s operations as a whole and for the purpose of evaluating financial performance and allocating resources, the CODM reviews financial information presented on a consolidated basis accompanied by information by customer and geographic region.

Geographic Revenue

The following table sets forth the Company’s revenue by geographic region for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands)
Hong Kong	$	56,485	$	78,628	$	104,890	$	144,318
Europe		3,282		1,513		8,634		3,703
United States		2,327		1,360		4,174		2,566
Asia Pacific		1,953		832		3,236		1,316
North America other than United States		1,095		1,860		1,365		3,303
Total revenue	$	65,142	$	84,193	$	122,299	$	155,206

As of July 31, 2016, substantially all of the Company’s property and equipment, net were located in the United States and Asia Pacific region with approximate net amount of $1.6 million and $1.5 million, respectively.

Major Customers

The customers representing 10% or more of revenue and accounts receivable were Wintech, the Company’s logistics provider, and Chicony, a direct ODM customer, which combined accounted for approximately 84% and 91% of total revenue for the three months ended July 31, 2016 and 2015, respectively. The only customer representing 10% or more of revenue and accounts receivable for the six months ended July 31, 2016 was Wintech, which accounted for approximately 73% of total revenue. The customers representing 10% or more of revenue and accounts receivable for the six months ended July 31, 2015 were Wintech and Chicony, which combined accounted for approximately 91% of total revenue. Accounts receivable with these two customers combined accounted for approximately $28.2 million and $32.5 million as of July 31, 2016 and January 31, 2016, respectively.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8971-108599

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8595-108599

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8984-108599

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e9054-108599

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8538-108599

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 29
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8864-108599

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=68060357&loc=d3e8906-108599

+ Details

Related-Party Transactions	6 Months Ended
Related-Party Transactions	Jul. 31, 2016
Related Party Transactions [Abstract]
Related-Party Transactions	15. Related-Party Transactions The Company considers an entity to be a related party if it owns more than 10% of the Company’s total voting stock at the end of each reporting period or if an officer or employee of an entity also serves on the Company’s board of directors or if it is a significant shareholder and has material business transactions with the Company. The Company leases software licenses with Cadence Design Systems, Inc. (“Cadence”). A member of the Company’s Board of Directors is also the Chief Executive Officer, President and a Director of Cadence. As of July 31, 2016, the Company committed to pay an aggregate amount of $1.6 million for these licenses through January 2017. The Company paid $0.7 million and $0.6 million under these agreements for the three months ended July 31, 2016 and 2015, respectively. The Company paid $1.3 million and $1.4 million under these agreements for the six months ended July 31, 2016 and 2015, respectively. License expenses related to these agreements included in research and development expense were approximately $0.7 million for the three months ended July 31, 2016 and 2015, respectively. License expenses related to these agreements included in research and development expense were approximately $1.4 million for the six months ended July 31, 2016 and 2015, respectively. In addition to the related party transactions noted above, the Company recognized revenue from sales to Wintech, the Company’s logistics provider. Wintech, along with an affiliate, owned approximately 4.6% of the Company’s voting stock as of January 31, 2013, but has sold such stock and is no longer a significant shareholder of the Company as of July 31, 2016 and January 31, 2016, respectively. The Company recognized revenue from sales to Wintech of approximately $46.8 million and $59.8 million for the three months ended July 31, 2016 and 2015, respectively. The Company recognized revenue from sales to Wintech of approximately $88.9 million and $105.1 million for the six months ended July 31, 2016 and 2015, respectively. As of July 31, 2016 and January 31, 2016, the Company had receivables from Wintech of approximately $20.4 million and $20.6 million, respectively.

Organization and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jul. 31, 2016
Accounting Policies [Abstract]
Organization	Organization Ambarella, Inc. (the “Company”) was incorporated in the Cayman Islands on January 15, 2004. The Company is a developer of semiconductor processing solutions for video that enable high-definition video capture, sharing and display. The Company combines its processor design capabilities with its expertise in video and image processing, algorithms and software to provide a technology platform that is designed to be easily scalable across multiple applications and enable rapid and efficient product development. The Company’s system-on-a-chip, or SoC, designs fully integrate high-definition video processing, image processing, audio processing and system functions onto a single chip, delivering exceptional video and image quality, differentiated functionality and low power consumption. The Company sells its solutions to leading original design manufacturers, or ODMs, and original equipment manufacturers, or OEMs, globally.
Basis of presentation	Basis of presentation The accompanying unaudited condensed consolidated financial statements have been prepared by the Company in accordance with the instructions to Form 10-Q pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and notes normally provided in audited financial statements. The accounting policies are described in the “Notes to Consolidated Financial Statements” in the Annual Report on Form 10-K for the 2016 fiscal year filed with the SEC on March 25, 2016 (the “Form 10-K”) and updated, as necessary, in this Form 10-Q. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from audited financial statements, but does not include all disclosures required by generally accepted accounting principles in the United States (“U.S. GAAP”). In the opinion of management, all adjustments (consisting of normal recurring accruals and adjustments) considered necessary for a fair statement have been included. The results of operations for any interim period are not necessarily indicative of, nor comparable to, the results of operations for any other interim period or for a full fiscal year. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes contained in the Form 10-K.
Basis of Consolidation	Basis of Consolidation The Company’s fiscal year ends on January 31. The condensed consolidated financial statements of the Company and its subsidiaries have been prepared in conformity with U.S. GAAP. All intercompany transactions and balances have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expense during the reported periods. Actual results could differ from those estimates. On an ongoing basis, management evaluates its estimates and assumptions, including those related to (i) the collectibility of accounts receivable; (ii) write down of excess and obsolete inventories; (iii) intangible assets and goodwill; (iv) the estimated useful lives of long-lived assets; (v) impairment of long-lived assets and financial instruments; (vi) warranty obligations; (vii) the valuation of stock-based compensation awards and financial instruments; (viii) the probability of performance objectives achievement; (ix) the realization of tax assets and estimates of tax liabilities, including reserves for uncertain tax positions; and (x) the recognition and disclosure of contingent liabilities. These estimates and assumptions are based on historical experience and on various other factors which the Company believes to be reasonable under the circumstances. The Company may engage third-party valuation specialists to assist with estimates related to the valuation of financial instruments and assets associated with various contractual arrangements. Such estimates often require the selection of appropriate valuation methodologies and significant judgment. Actual results could differ from these estimates under different assumptions or circumstances.
Concentration of Risk	Concentration of Risk The Company’s products are manufactured, assembled and tested by third-party contractors located primarily in Asia. The Company does not have long-term agreements with these contractors. A significant disruption in the operations of one or more of these contractors would impact the production of the Company’s products which could have a material adverse effect on its business, financial condition and results of operations. A substantial portion of the Company’s revenue is derived from sales through its logistics provider, Wintech Microelectronics Co., Ltd., or Wintech, which serves as its non-exclusive sales representative in Asia other than Japan, and through one large direct ODM customer, Chicony Electronics Co., Ltd., or Chicony. Termination of the relationships with these two customers could result in a temporary or permanent loss of revenue and termination of the relationship with Wintech could result in an obligation to repurchase unsold product. Furthermore, any credit issues from these two customers could impair their abilities to make timely payment to the Company. See Note 14 for additional information regarding concentration with these two customers. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, marketable securities and accounts receivable. The Company maintains its cash primarily in checking and money market accounts with reputable financial institutions. Cash deposits held with these financial institutions may exceed the amount of insurance provided on such deposits. The Company has not experienced any material losses on deposits of its cash. The cash equivalents and marketable securities consist primarily of money market funds, asset-backed securities, commercial paper, U.S. government securities, agency bonds and debt securities of corporations which management assesses to be highly liquid, in order to limit the exposure of each investment. The Company does not hold or issue financial instruments for trading purposes. The Company performs ongoing credit evaluations of each of its customers and adjusts credit limits based upon payment history and the customer’s credit worthiness. The Company regularly monitors collections and payments from its customers.
Cash Equivalents and Marketable Securities	Cash Equivalents and Marketable Securities The Company considers all highly liquid investments with original maturities of less than three months at the time of purchase to be cash equivalents. Investments that are highly liquid with original maturities at the time of purchase greater than three months are considered as marketable securities. The Company classifies these investments as “available-for-sale” securities carried at fair value, based on quoted market prices of similar assets, with the unrealized gains or losses reported, net of tax, as a separate component of shareholders’ equity and included in accumulated other comprehensive income (loss) in the condensed consolidated balance sheets. The amortization of security premiums and accretion of discounts and the realized gains and losses are both recorded in other income (loss), net in the condensed consolidated statements of operations. The Company reviews its investments for possible other-than-temporary impairments on a regular basis. If any loss on investment is believed to be other-than-temporary, a charge will be recorded and a new cost basis in the investment will be established. In evaluating whether a loss on a security is other-than-temporary, the Company considers the following factors: 1) general market conditions, 2) the duration and extent to which the fair value is less than cost, 3) the Company’s intent and ability to hold the investment. For securities in an unrealized loss position which is deemed to be other-than-temporary, the difference between the security’s then-current amortized cost basis and fair value is separated into (i) the amount of the impairment related to the credit loss (i.e., the credit loss component) and (ii) the amount of the impairment related to all other factors (i.e., the non-credit loss component). The credit loss component is recognized in earnings. The non-credit loss component is recognized in accumulated other comprehensive income (loss). Due to the relative short term nature of the investments, there have been no other-than-temporary impairments recorded to date.
Inventories	Inventories The Company records inventories at the lower of cost or market. The cost includes materials and other production costs and is computed using standard cost on a first-in, first-out basis. Inventory reserves are recorded for estimated obsolescence or unmarketable inventories based on forecast of future demand and market conditions. If actual market conditions are less favorable than projected, or if future demand for the Company’s products decrease, additional inventory write-downs may be required. Once inventory is written down, a new accounting cost basis is established and, accordingly, any associated reserve is not reversed until the inventory is sold or scrapped. There were no material inventory losses recognized for the three and six months ended July 31, 2016 and 2015, respectively.
Business Combinations and Intangible Assets	Business Combinations and Intangible Assets The Company allocates the fair value of purchase price to the assets acquired and liabilities assumed based on their estimated fair values. The excess of the fair value of purchase price over the fair values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair values of assets acquired and liabilities assumed, especially with respect to intangible assets, management makes significant estimates and assumptions. Critical estimates in valuing certain intangible assets include, but are not limited to, replacement cost. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates.
Goodwill and In-Process Research and Development	Goodwill and In-Process Research and Development Goodwill and in-process research and development (“IPR&D”) are required to be tested for impairment at least annually or sooner whenever events or changes in circumstances indicate that the assets may be impaired. The Company has a single reporting unit for goodwill impairment test purposes based on its business and reporting structure. The Company does not amortize goodwill. Acquired IPR&D is capitalized at fair value as an intangible asset and amortization commences upon completion of the underlying projects. When a project underlying reported IPR&D is completed, the corresponding amount of IPR&D is reclassified as an amortizable purchased intangible asset and is amortized over its estimated useful life.
Revenue Recognition	Revenue Recognition The Company generates revenue from the sales of its SoCs to OEMs or ODMs, either directly or through logistics providers. Revenue from sales directly to OEMs and ODMs is recognized upon shipment provided persuasive evidence of an arrangement exists, legal title to the products and risk of ownership have transferred, the fee is fixed or determinable, and collection of the resulting receivable is reasonably assured. The Company provides its logistics providers with the rights to return excess levels of inventory and to future price adjustments. Given the inability to reasonably estimate these price changes and returns, revenue and costs related to shipments to logistics providers are deferred until the Company has received notification from its logistics providers that they have sold the Company’s products. Information reported by the Company’s logistics providers includes product resale price, quantity and end customer shipment information as well as remaining inventory on hand. At the time of shipment to a logistics provider, the Company records a trade receivable as there is a legally enforceable right to receive payment, reduces inventory for the value of goods shipped as legal title has passed to the logistics provider and defers the related margin as deferred revenue in the condensed consolidated balance sheets. Any price adjustments are recorded as a change to deferred revenue at the time the adjustments are agreed upon. Arrangements with certain OEM customers provide for pricing that is dependent upon the end products into which the Company’s SoCs are used. These arrangements may also entitle the Company to a share of the product margin ultimately realized by the OEM. The minimum guaranteed amount of revenue related to the sale of products subject to these arrangements is recognized when all other elements of revenue recognition are met. Any amounts at the date of shipment invoiced in excess of the minimum guaranteed contract price are deferred until the additional amounts the Company is entitled to are fixed or determinable. Additional amounts earned by the Company resulting from margin sharing arrangements and determination of the end products into which the products are ultimately incorporated are recognized when end customer sales volume is reported to the Company. The Company also enters into engineering service agreements with certain customers. These agreements may include multiple deliverables, such as software development services, licensing of intellectual property and post-contract customer support, or PCS. The Company does not sell separately any of these components and does not have Vendor Specific Objective Evidence, or VSOE, for the deliverables. Accordingly, revenues from these agreements are deferred for any amounts billed until delivery of all the elements. If the agreements include PCS, the revenues are recognized ratably over the estimated supporting periods. The revenue from engineering service agreements was not material for the three and six months ended July 31, 2016 and 2015, respectively.
Cost of Revenue	Cost of Revenue Cost of revenue includes cost of materials, cost associated with packaging and assembly, testing and shipping, cost of personnel, stock-based compensation, logistics and quality assurance, warranty cost, royalty expense, write-downs of inventories and allocation of overhead.
Income Taxes	Income Taxes The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements or tax returns. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized. The Company applies authoritative guidance for the accounting for uncertainty in income taxes. The guidance requires that tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. Upon estimating the Company’s tax positions and tax benefits, the Company considered and evaluated numerous factors, which may require periodic adjustments and which may not reflect the final tax liabilities. The Company adjusts its financial statements to reflect only those tax positions that are more likely than not to be sustained under examination. As part of the process of preparing condensed consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differing treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets, which are included in the condensed consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the condensed consolidated statements of operations become deductible expenses under applicable income tax laws, or loss or credit carryforwards are utilized. In assessing whether deferred tax assets may be realized, management considers whether it is more likely than not that some portion or all of deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income. The Company makes estimates and judgments about its future taxable income based on assumptions that are consistent with its plans and estimates. Should the actual amounts differ from estimates, the amount of valuation allowance could be materially impacted. Any adjustment to the deferred tax asset valuation allowance would be recorded in the condensed consolidated income statement for the periods in which the adjustment is determined to be required.
Net Income Per Ordinary Share	Net Income Per Ordinary Share Basic earnings per share is computed by dividing net income available to ordinary shareholders by the weighted-average number of ordinary shares outstanding during the period. Diluted earnings per share is computed by dividing net income available to ordinary shareholders by the weighted-average number of ordinary shares outstanding during the period increased to include the number of additional ordinary shares that would have been outstanding if the potentially dilutive securities had been issued. Potentially dilutive securities include outstanding stock options, shares to be purchased under the Company’s employee stock purchase plan, unvested restricted stock and restricted stock units. The dilutive effect of potentially dilutive securities is reflected in diluted earnings per share by application of the treasury stock method.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) includes unrealized gains or losses from available-for-sale securities that are excluded from net income.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”). The new guidance clarifies the principles and develops a common revenue recognition guidance for U.S. GAAP and International Financial Reporting Standards (the “IFRS”). Under the new guidance, an entity is required to recognize an amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The original effective date of the ASU would have required the public companies to adopt the standard for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. In July 2015, the FASB voted to amend the ASU by approving a one-year deferral of the effective date as well as providing the option to early adopt the standard on the original effective date. The deferral results in this new revenue standard being effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606) – Principal versus Agent Considerations (“ASU 2016-08”), which clarifies the implementation guidance for principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606) – Identifying Performance Obligations and Licensing (“ASU 2016-10”), which amends the guidance in ASU 2014-09 related to identifying performance obligations and accounting for licenses of intellectual property. Accordingly, the Company must adopt ASU 2016-08 and ASU 2016-10 with ASU 2014-09 in its first quarter of fiscal year 2019. The new revenue guidance may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact of adoption on its financial position, results of operations and disclosures. In August 2014, the FASB issued ASU No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. In connection with each annual and interim period, management is required to assess whether there is substantial doubt about an entity’s ability to continue as a going concern within one year after the issuance date, and to provide related footnote disclosures in certain circumstances. The new guidance is effective for annual periods ending after December 15, 2016, and interim periods within annual periods beginning after December 15, 2016. Early adoption is permitted. This ASU is not expected to have an impact on the Company’s financial statements or disclosures. In July 2015, the FASB issued ASU No. 2015-11, Simplifying the Measurement of Inventory. The new guidance changes the measurement principle for inventory from the lower of cost or market to 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. It applies to entities that measure inventory using a method other than last-in, first-out (“LIFO”) and the retail inventory method (“RIM”). The new guidance will be effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years and should be applied prospectively. Early adoption is permitted as of the beginning of an interim or annual reporting period. The Company is currently evaluating the impact of adoption on its financial position, results of operations and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). This standard requires entities that lease assets to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. The standard is effective for fiscal years and the interim periods within those fiscal years beginning after December 15, 2018. The guidance is required to be applied by the modified retrospective transition approach. Early adoption is permitted. The Company is currently assessing the impact of the adoption of this new guidance on its financial position, results of operations and disclosures. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting, to simplify and improve the accounting for employee share-based awards. The new standard amends the accounting for employee share-based payment transactions to require recognition of the tax effects resulting from the settlement of stock-based awards as income tax benefit or expense in the income statement in the reporting period in which they occur. In addition, the tax-related cash flows resulting from share-based payments will be classified as cash flows from operating activities and cash payments made to the taxing authorities on the employees’ behalf for withheld shares will be classified as financing activities on the statement of cash flows. The new guidance also provides an accounting policy election to account for forfeitures as they occur. The new guidance is effective for public entities for annual reporting periods beginning after December 15, 2016, and interim periods within that reporting period. Early adoption is permitted with any adjustments reflected as of the beginning of the fiscal year of adoption. The Company elected to early adopt this new guidance in the first quarter of its fiscal year 2017. As a result of this adoption, the Company recorded an increase to retained earnings of $11.7 million to recognize U.S. net operating loss carryforwards attributable to tax benefits from excess stock-based compensation that had not been previously recognized and recorded a decrease to retained earnings of $0.2 million resulting from the election of accounting policy to account for forfeitures as they occur as of February 1, 2016. The Company also elected to apply the presentation for cash flows related to excess tax benefits prospectively. The presentation requirements for cash flows related to employee taxes paid for withheld shares has no impact on the Company’s condensed consolidated statements of cash flows. On February 1, 2016, the cumulative effect adjustment of these changes recognized in the beginning of retained earnings was approximately $11.5 million. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326), to introduce a new impairment model for recognizing credit losses on financial instruments based on an estimated of current expected credit losses (ECL). Under the new model, available-for-sale (AFS) debt securities are required to estimate ECL only when the fair value is below the amortized cost of the asset and is no longer based on an impairment being “other-than-temporary”. The new model also requires the impairment calculation on an individual security level and requires an entity use present value of cash flows when estimating the ECL. The credit-related losses are required to be recognized through earnings and non-credit related losses are reported in other comprehensive income. The ASU will be effective for public entities in fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. The new guidance will require modified retrospective application to all outstanding instruments, with a cumulative effect adjustment recorded to opening retained earnings as of the beginning of the first period in which the guidance becomes effective. The Company does not believe the adoption of this new guidance will have material impact on its consolidated financial statements.

Financial Instruments and Fair Value (Tables)

6 Months Ended

Jul. 31, 2016

Investments All Other Investments [Abstract]

Schedule of Available-for-Sale Securities at Fair Value

All of the investments are classified as available-for-sale securities and reported at fair value in the condensed consolidated balance sheets as follows:

	As of July 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market funds	$	103	$	—	$	—		$	103
Demand deposit		10,000		—		—			10,000
Commercial paper		7,479		—		—			7,479
Corporate bonds		19,342		17		(2	)		19,357
Asset-backed securities		8,446		6		—			8,452
U.S. government securities		13,197		11		—			13,208
Agency bonds		2,023		1		—			2,024
Total cash equivalents and marketable securities	$	60,590	$	35	$	(2	)	$	60,623

	As of January 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
Money market funds	$	530	$	—	$	—		$	530
Commercial paper		2,598		—		—			2,598
Corporate bonds		21,342		7		(9	)		21,340
Asset-backed securities		4,586		—		(1	)		4,585
U.S. government securities		9,274		4		(6	)		9,272
Agency bonds		2,044		—		(2	)		2,042
Total cash equivalents and marketable securities	$	40,374	$	11	$	(18	)	$	40,367

Schedule of Cash Equivalents and Marketable Securities

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Included in cash equivalents	$	10,103	$	530
Included in marketable securities		50,520		39,837
Total cash equivalents and marketable securities	$	60,623	$	40,367

Summary of Contractual Maturities of Investments

The contractual maturities of the investments at July 31, 2016 and January 31, 2016 were as follows:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Due within one year	$	52,856	$	33,449
Due within one to two years		7,767		6,918
Total cash equivalents and marketable securities	$	60,623	$	40,367

Schedule of Fair Value of Financial Instruments Measured on Recurring Basis

The following table presents the fair value of the financial instruments measured on a recurring basis as of July 31, 2016 and January 31, 2016:

	As of July 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	103	$	103	$	—	$	—
Demand deposit		10,000		10,000		—
Commercial paper		7,479		—		7,479		—
Corporate bonds		19,357		—		19,357		—
Asset-backed securities		8,452		—		8,452		—
U.S. government securities		13,208		—		13,208		—
Agency bonds		2,024		—		2,024		—
Total cash equivalents and marketable securities	$	60,623	$	10,103	$	50,520	$	—

	As of January 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Money market funds	$	530	$	530	$	—	$	—
Commercial paper		2,598		—		2,598		—
Corporate bonds		21,340		—		21,340		—
Asset-backed securities		4,585		—		4,585		—
U.S. government securities		9,272		—		9,272		—
Agency bonds		2,042		—		2,042		—
Total cash equivalents and marketable securities	$	40,367	$	530	$	39,837	$	—

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Inventories (Tables)

6 Months Ended

Jul. 31, 2016

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Work-in-progress	$	11,944	$	9,474
Finished goods		8,954		8,693
Total	$	20,898	$	18,167

Property and Equipment, Net (Tables)

6 Months Ended

Jul. 31, 2016

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016			January 31, 2016
	(in thousands)
Computer equipment and software	$	6,700		$	6,421
Machinery and equipment		3,004			2,706
Furniture and fixtures		794			492
Leasehold improvements		1,550			1,429
Construction in progress		195			253
		12,243			11,301
Less: accumulated depreciation and amortization		(8,601	)		(7,853	)
Total property and equipment, net	$	3,642		$	3,448

Accrued Liabilities (Tables)

6 Months Ended

Jul. 31, 2016

Payables And Accruals [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Accrued employee compensation	$	11,806	$	14,512
Accrued warranty		200		234
Accrued rebates		1,191		824
Accrued product development costs		7,544		6,339
Other accrued liabilities		2,382		1,869
Total accrued liabilities	$	23,123	$	23,778

Deferred Revenue and Deferred Cost (Tables)

6 Months Ended

Jul. 31, 2016

Deferred Revenue Disclosure [Abstract]

Schedule of Deferred Revenue and Related Cost

Deferred revenue and related cost at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016			January 31, 2016
	(in thousands)
Deferred revenue on product shipments	$	6,048		$	12,201
Deferred revenue from licenses & services		1,957			1,653
Deferred cost of revenue on product shipments		(2,541	)		(3,777	)
Total deferred revenue, net	$	5,464		$	10,077

Other Long-Term Liabilities (Tables)

6 Months Ended

Jul. 31, 2016

Other Liabilities Disclosure [Abstract]

Schedule of Other Long-Term Liabilities

Other long-term liabilities at July 31, 2016 and January 31, 2016 consisted of the following:

	As of
	July 31, 2016		January 31, 2016
	(in thousands)
Unrecognized tax benefits, including interest	$	1,427	$	10,917
Deferred tax liabilities, non-current		1,364		1,423
Other long-term liabilities		2		2
Total other long-term liabilities	$	2,793	$	12,342

Capital Stock (Tables)

6 Months Ended

Jul. 31, 2016

Equity [Abstract]

Schedule of Ordinary Shares Reserved for Future Issuance under EIP and ESPP

As of July 31, 2016 and January 31, 2016, the following ordinary shares were reserved for future issuance under the EIP and ESPP:

	As of
	July 31, 2016		January 31, 2016
Shares reserved for options, restricted stock and restricted stock units		5,791,467		5,027,475
Shares reserved for employee stock purchase plan		1,320,582		974,273

Stock-based Compensation (Tables)

6 Months Ended

Jul. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Classification of Stock-based Compensation

The following table presents the classification of stock-based compensation for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands)
Stock-based compensation:
Cost of revenue	$	246	$	127	$	491	$	251
Research and development		6,873		3,671		13,592		6,765
Selling, general and administrative		4,347		2,323		8,684		4,587
Total stock-based compensation	$	11,466	$	6,121	$	22,767	$	11,603

Weighted-Average Assumptions Used to Estimate Fair Value

The following table sets forth the weighted-average assumptions used to estimate the fair value of stock options and employee stock purchase plan awards for the periods indicated:

	Three Months Ended July 31,						Six Months Ended July 31,
	2016			2015			2016			2015
Stock Options:
Volatility		38	%		57	%		38	%		59	%
Risk-free interest rate		1.39	%		1.85	%		1.55	%		1.76	%
Expected term (years)	6.08				6.08		5.96				6.08
Dividend yield		0	%		0	%		0	%		0	%
Employee stock purchase plan awards:
Volatility		—			—			67	%		63	%
Risk-free interest rate		—			—			0.52	%		0.15	%
Expected term (years)		—			—			0.5			0.5
Dividend yield		—			—			0	%		0	%

Stock Option Activities

The following table summarizes stock option activities for the six months ended July 31, 2016:

	Option Outstanding
										Weighted-
								Total Intrinsic		Average
						Weighted-		Value of		Remaining		Aggregate
				Weighted-		Average		options		Contractual		Intrinsic
				Average		Grant-date		Exercised		Term		Value
	Shares			Exercise Price		Fair Value		(in thousands)		(in years)		(in thousands)
Outstanding at January 31, 2016		1,853,390		$	19.36
Granted		78,700			41.93	$	16.38
Exercised		(65,836	)		10.96			$	2,176
Forfeited		(8,625	)		52.43
Expired		(7,721	)		14.12
Outstanding at July 31, 2016		1,849,908			20.48					5.59		$	71,725
Exercisable at July 31, 2016		1,430,350		$	13.00						4.75	$	65,004

Restricted Stock Activities

The following table summarizes restricted stock activities for the periods indicated:

				Weighted-
				Average
				Grant-Date
	Shares			Fair Value
Unvested at January 31, 2016		2,495,488		$	47.04
Granted		25,504			43.64
Vested		(464,699	)		35.56
Forfeited		(11,703	)		46.10
Unvested at July 31, 2016		2,044,590		$	48.03

Net Income Per Ordinary Share (Tables)

6 Months Ended

Jul. 31, 2016

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Income Per Ordinary Share

The following table sets forth the computation of basic and diluted net income per ordinary share for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands, except share and per share data)
Numerator:
Net income	$	8,632	$	23,097	$	10,415	$	41,951
Less: amount allocable to unvested early exercised options		—		—		—		—
Net income allocable to ordinary shareholders - basic	$	8,632	$	23,097	$	10,415	$	41,951
Undistributed earnings reallocated to ordinary shareholders		—		—		—		—
Net income allocable to ordinary shareholders - diluted	$	8,632	$	23,097	$	10,415	$	41,951
Denominator:
Weighted-average ordinary shares outstanding		32,557,398		31,515,446		32,492,723		31,307,292
Less: weighted-average unvested early exercised options subject to repurchase		—		—		—		(56	)
Weighted-average ordinary shares - basic		32,557,398		31,515,446		32,492,723		31,307,236
Effect of potentially dilutive securities:
Employee stock options		1,074,331		1,351,924		1,062,310		1,374,810
Restricted stock and restricted stock units		530,279		1,028,899		498,128		995,092
Employee stock purchase plan		13,458		7,953		9,942		11,101
Weighted-average ordinary shares - diluted		34,175,466		33,904,222		34,063,103		33,688,239
Net income per ordinary share:
Basic	$	0.27	$	0.73	$	0.32	$	1.34
Diluted	$	0.25	$	0.68	$	0.31	$	1.25

Weighted-Average Potentially Dilutive Securities Excluded from Computation of Diluted Net Income Per Ordinary Share

The following weighted-average potentially dilutive securities were excluded from the computation of diluted net income per ordinary share as their effect would have been antidilutive:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
Options to purchase ordinary shares		471,534		13,081		476,116		42,257
Restricted stock and restricted stock units		893,341		93,002		1,047,630		46,501
Employee stock purchase plan		—		—		17,191		6,714
Early exercised options subject to repurchase		—		—		—		56
		1,364,875		106,083		1,540,937		95,528

Income Taxes (Tables)

6 Months Ended

Jul. 31, 2016

Income Tax Disclosure [Abstract]

Summary of Income Taxes

The following table provides details of income taxes for the periods indicated:

	Three Months Ended July 31,						Six Months Ended July 31,
	2016			2015			2016			2015
	(in thousands)
Income before income taxes	$	9,433		$	25,048		$	10,808		$	45,400
Provision for income taxes		801			1,951			393			3,449
Effective tax rate	8.5		%		7.8	%	3.6		%		7.6	%

Commitments and Contingencies (Tables)

6 Months Ended

Jul. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Future Annual Minimum Lease Payments

Future annual minimum payments under these operating leases with initial lease terms in excess of one year are as follows:

	As of
	July 31, 2016
Fiscal Year	(in thousands)
2017	$	3,533
2018		2,662
2019		1,955
2020		1,531
2021		515
Total future annual minimum lease payments	$	10,196

Segment Reporting (Tables)

6 Months Ended

Jul. 31, 2016

Segment Reporting [Abstract]

Company's Revenue by Geographic Region

The following table sets forth the Company’s revenue by geographic region for the periods indicated:

	Three Months Ended July 31,				Six Months Ended July 31,
	2016		2015		2016		2015
	(in thousands)
Hong Kong	$	56,485	$	78,628	$	104,890	$	144,318
Europe		3,282		1,513		8,634		3,703
United States		2,327		1,360		4,174		2,566
Asia Pacific		1,953		832		3,236		1,316
North America other than United States		1,095		1,860		1,365		3,303
Total revenue	$	65,142	$	84,193	$	122,299	$	155,206

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - Accounting Standards Update (ASU) 2016-09 [Member] $ in Millions	Feb. 01, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment of changes recognized in beginning of retained earnings	$ 11.5
Cumulative effect adjustment of changes recognized in beginning of retained earnings as a result of adoption of new guidance for tax benefits that were not previously recognized [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment of changes recognized in beginning of retained earnings	11.7
Cumulative effect adjustment of changes recognized in beginning of retained earnings as a result of adoption of new guidance for accounting for forfeitures as they occur [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect adjustment of changes recognized in beginning of retained earnings	$ (0.2)

- Definition

Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

+ References + Details

Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 60,590	$ 40,374
Unrealized Gains	35	11
Unrealized Losses	(2)	(18)
Fair Value	60,623	40,367
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	103	530
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	103	530
Demand deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,000
Unrealized Gains	0
Unrealized Losses	0
Fair Value	10,000
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,479	2,598
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	7,479	2,598
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,342	21,342
Unrealized Gains	17	7
Unrealized Losses	(2)	(9)
Fair Value	19,357	21,340
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,446	4,586
Unrealized Gains	6	0
Unrealized Losses	0	(1)
Fair Value	8,452	4,585
U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,197	9,274
Unrealized Gains	11	4
Unrealized Losses	0	(6)
Fair Value	13,208	9,272
Agency bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,023	2,044
Unrealized Gains	1	0
Unrealized Losses	0	(2)
Fair Value	$ 2,024	$ 2,042

Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 60,623	$ 40,367
Included in cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	10,103	530
Included in marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash equivalents and marketable securities	$ 50,520	$ 39,837

Financial Instruments and Fair Value - Summary of Contractual Maturities of Investments (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Available For Sale Securities Debt Maturities Fair Value [Abstract]
Due within one year	$ 52,856	$ 33,449
Due within one to two years	7,767	6,918
Total cash equivalents and marketable securities	$ 60,623	$ 40,367

Inventories - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Inventory Disclosure [Abstract]
Work-in-progress	$ 11,944	$ 9,474
Finished goods	8,954	8,693
Total	$ 20,898	$ 18,167

Property and Equipment, Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 12,243	$ 11,301
Less: accumulated depreciation and amortization	(8,601)	(7,853)
Total property and equipment, net	3,642	3,448
Computer equipment and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,700	6,421
Machinery and equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,004	2,706
Furniture and fixtures [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	794	492
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,550	1,429
Construction in progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 195	$ 253

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)		3 Months Ended		6 Months Ended
	Jun. 25, 2015	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015	Jan. 31, 2016
Finite Lived Intangible Assets [Line Items]
Goodwill		$ 26,601,000		$ 26,601,000		$ 26,601,000
Impairment of goodwill or intangible assets		0	$ 0	0	$ 0
IPR&D
Finite Lived Intangible Assets [Line Items]
Amortization of intangible asset		$ 0		$ 0
Vis Lab S R L
Finite Lived Intangible Assets [Line Items]
Business acquisition date	Jun. 25, 2015
Cash paid for business acquisition	$ 30,000,000
Goodwill	25,300,000
Intangible assets acquired	4,100,000
Net assets acquired	600,000
Deferred tax liabilities, intangible assets	$ 1,300,000

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Payables And Accruals [Abstract]
Accrued employee compensation	$ 11,806	$ 14,512
Accrued warranty	200	234
Accrued rebates	1,191	824
Accrued product development costs	7,544	6,339
Other accrued liabilities	2,382	1,869
Total accrued liabilities	$ 23,123	$ 23,778

Deferred Revenue and Deferred Cost - Schedule of Deferred Revenue and Related Cost (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Deferred Revenue Disclosure [Abstract]
Deferred revenue on product shipments	$ 6,048	$ 12,201
Deferred revenue from licenses & services	1,957	1,653
Deferred cost of revenue on product shipments	(2,541)	(3,777)
Total deferred revenue, net	$ 5,464	$ 10,077

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References + Details

Other Long-Term Liabilities - Schedule of Other Long-Term Liabilities (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Other Liabilities Disclosure [Abstract]
Unrecognized tax benefits, including interest	$ 1,427	$ 10,917
Deferred tax liabilities, non-current	1,364	1,423
Other long-term liabilities	2	2
Total other long-term liabilities	$ 2,793	$ 12,342

Other Long-Term Liabilities - Additional Information (Detail) - Accounting Standards Update (ASU) 2016-09 [Member] $ in Millions	Feb. 01, 2016 USD ($)
Other Liabilities Noncurrent [Line Items]
Cumulative effect adjustment of changes recognized in beginning of retained earnings as a result of adoption of new guidance for tax benefits that were not previously recognized	$ 11.7
Unrecognized tax benefits reduced as a result of adoption of new accounting guidance	$ 9.5

Capital Stock - Additional Information (Detail) - USD ($)			6 Months Ended
	May 31, 2016	Feb. 01, 2016	Jul. 31, 2016	Jul. 31, 2015	Jan. 31, 2016
Class Of Stock [Line Items]
Preference shares, shares authorized			20,000,000		20,000,000
Preference shares, par value			$ 0.00045		$ 0.00045
Preference shares, shares issued			0		0
Preference shares, shares outstanding			0		0
Ordinary shares, shares authorized			200,000,000		200,000,000
Stock repurchase program, period	6 months
Stock repurchased during period, shares			405,089
Stock repurchased during period, cash			$ 20,183,000	$ 0
Maximum [Member]
Class Of Stock [Line Items]
Amount authorized under stock repurchase program	$ 75,000,000
2012 Equity Incentive Plan [Member]
Class Of Stock [Line Items]
Additional ordinary shares reserved for issuance		1,455,001
2012 Equity Incentive Plan [Member] \| Scenario, plan automatically increased by the lessor of [Member]
Class Of Stock [Line Items]
Annual increase in ordinary shares for available for future issuance		3,500,000
Annual shares increase for future issuance by percentage under 2012 equity incentive plan		4.50%
Amended and Restated 2012 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Additional ordinary shares reserved for issuance		404,166
Amended and Restated 2012 Employee Stock Purchase Plan [Member] \| Scenario, plan automatically increased by the lessor of [Member]
Class Of Stock [Line Items]
Annual increase in ordinary shares for available for future issuance		1,500,000
Annual shares increase for future issuance by percentage under 2012 employee stock purchase plan		1.25%

Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance under EIP and ESPP (Detail) - shares	Jul. 31, 2016	Jan. 31, 2016
Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved	5,791,467	5,027,475
Employee stock purchase plan awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved	1,320,582	974,273

Stock-based Compensation - Classification of Stock-based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Stock-based compensation:
Total stock-based compensation	$ 11,466	$ 6,121	$ 22,767	$ 11,603
Cost of revenue [Member]
Stock-based compensation:
Total stock-based compensation	246	127	491	251
Research and development [Member]
Stock-based compensation:
Total stock-based compensation	6,873	3,671	13,592	6,765
Selling, general and administrative [Member]
Stock-based compensation:
Total stock-based compensation	$ 4,347	$ 2,323	$ 8,684	$ 4,587

Stock-based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions	6 Months Ended
	Jul. 31, 2016 USD ($) $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of ordinary shares \| $ / shares	$ 57.98
Stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost, stock options	$ 10.0
Weighted average recognition period	2 years 1 month 28 days
Restricted stock units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost, restricted stock units	$ 81.2
Weighted average recognition period	2 years 9 months 26 days
Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average recognition period	2 years 22 days
Total unrecognized compensation cost, restricted stock awards	$ 9.5
Aggregate intrinsic value of unvested restricted stock	$ 118.5

Stock-based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value (Detail)	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility	38.00%	57.00%	38.00%	59.00%
Risk-free interest rate	1.39%	1.85%	1.55%	1.76%
Expected term (years)	6 years 29 days	6 years 29 days	5 years 11 months 16 days	6 years 29 days
Dividend yield	0.00%	0.00%	0.00%	0.00%
Employee stock purchase plan awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility	0.00%	0.00%	67.00%	63.00%
Risk-free interest rate	0.00%	0.00%	0.52%	0.15%
Expected term (years)	0 years	0 years	6 months	6 months
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-based Compensation - Stock Option Activities (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jul. 31, 2016 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding \| shares	1,853,390
Shares, Granted \| shares	78,700
Shares, Exercised \| shares	(65,836)
Shares, Forfeited \| shares	(8,625)
Shares, Expired \| shares	(7,721)
Shares, Outstanding \| shares	1,849,908
Shares, Exercisable \| shares	1,430,350
Weighted-Average Exercise Price, Outstanding	$ 19.36
Weighted-Average Exercise Price, Granted	41.93
Weighted-Average Exercise Price, Exercised	10.96
Weighted-Average Exercise Price, Forfeited	52.43
Weighted-Average Exercise Price, Expired	14.12
Weighted-Average Exercise Price, Outstanding	20.48
Weighted-Average Exercise Price, Exercisable	13.00
Weighted-Average Grant-date Fair Value, Granted	$ 16.38
Total Intrinsic Value of options Exercised \| $	$ 2,176
Weighted-Average Remaining Contractual Term, Outstanding	5 years 7 months 2 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 9 months
Aggregate Intrinsic Value, Outstanding \| $	$ 71,725
Aggregate Intrinsic Value, Exercisable \| $	$ 65,004

Stock-based Compensation - Restricted Stock Activities (Detail) - Restricted stock [Member]	6 Months Ended
	Jul. 31, 2016 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested, beginning balance \| shares	2,495,488
Shares, Granted \| shares	25,504
Shares, Vested \| shares	(464,699)
Shares, Forfeited \| shares	(11,703)
Shares, Unvested, ending balance \| shares	2,044,590
Weighted-Average Grant-Date Fair Value, Unvested, beginning balance \| $ / shares	$ 47.04
Weighted-Average Grant-Date Fair Value, Granted \| $ / shares	43.64
Weighted-Average Grant-Date Fair Value, Vested \| $ / shares	35.56
Weighted-Average Grant-Date Fair Value, Forfeited \| $ / shares	46.10
Weighted-Average Grant-Date Fair Value, Unvested, ending balance \| $ / shares	$ 48.03

Net Income Per Ordinary Share - Computation of Basic and Diluted Net Income Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Numerator:
Net income	$ 8,632	$ 23,097	$ 10,415	$ 41,951
Less: amount allocable to unvested early exercised options	0	0	0	0
Net income allocable to ordinary shareholders - basic	8,632	23,097	10,415	41,951
Undistributed earnings reallocated to ordinary shareholders	0	0	0	0
Net income allocable to ordinary shareholders - diluted	$ 8,632	$ 23,097	$ 10,415	$ 41,951
Denominator:
Weighted-average ordinary shares outstanding	32,557,398	31,515,446	32,492,723	31,307,292
Less: weighted-average unvested early exercised options subject to repurchase	0	0	0	(56)
Weighted-average ordinary shares - basic	32,557,398	31,515,446	32,492,723	31,307,236
Effect of potentially dilutive securities:
Employee stock options	1,074,331	1,351,924	1,062,310	1,374,810
Restricted stock and restricted stock units	530,279	1,028,899	498,128	995,092
Employee stock purchase plan	13,458	7,953	9,942	11,101
Weighted-average ordinary shares - diluted	34,175,466	33,904,222	34,063,103	33,688,239
Net income per ordinary share:
Basic	$ 0.27	$ 0.73	$ 0.32	$ 1.34
Diluted	$ 0.25	$ 0.68	$ 0.31	$ 1.25

Net Income Per Ordinary Share - Weighted-Average Potentially Dilutive Securities Excluded from Computation of Diluted Net Income Per Ordinary Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	1,364,875	106,083	1,540,937	95,528
Options to purchase ordinary shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	471,534	13,081	476,116	42,257
Restricted stock and restricted stock units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	893,341	93,002	1,047,630	46,501
Employee stock purchase plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	0	0	17,191	6,714
Early exercised options subject to repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share	0	0	0	56

Income Taxes - Summary of Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Income Tax Disclosure [Abstract]
Income before income taxes	$ 9,433	$ 25,048	$ 10,808	$ 45,400
Provision for income taxes	$ 801	$ 1,951	$ 393	$ 3,449
Effective tax rate	8.50%	7.80%	3.60%	7.60%

Income Taxes - Additional Information (Detail) $ in Millions	6 Months Ended
	Jul. 31, 2016 USD ($)
Income Tax Disclosure [Abstract]
Decrease in income before income tax	$ 34.6
Increase in discrete tax benefits	1.1
Unrecognized tax benefits	$ 33.6

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015	Jan. 31, 2016
Loss Contingencies [Line Items]
Net operating lease expenses	$ 1,900,000	$ 1,700,000	$ 3,600,000	$ 3,600,000
Total manufacturing purchase commitments	31,000,000		31,000,000		$ 19,700,000
Indemnification agreement [Member]
Loss Contingencies [Line Items]
Payments under indemnification obligations			0		0
Liabilities recorded under indemnification obligations	$ 0		$ 0		$ 0

Commitments and Contingencies - Future Annual Minimum Lease Payments (Detail) $ in Thousands	Jul. 31, 2016 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2017	$ 3,533
2018	2,662
2019	1,955
2020	1,531
2021	515
Total future annual minimum lease payments	$ 10,196

Segment Reporting - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016 USD ($)	Jul. 31, 2015	Jul. 31, 2016 USD ($) Segment	Jul. 31, 2015	Jan. 31, 2016 USD ($)
Concentration Risk [Line Items]
Number of reportable segment \| Segment			1
Property and equipment, net	$ 3,642		$ 3,642		$ 3,448
Accounts receivable	33,588		33,588		39,408
Wintech And Chicony [Member]
Concentration Risk [Line Items]
Accounts receivable	$ 28,200		$ 28,200		$ 32,500
Sales revenue, net [Member] \| Wintech And Chicony [Member] \| Customer concentration risk [Member]
Concentration Risk [Line Items]
Percentage of revenue	84.00%	91.00%		91.00%
Sales revenue, net [Member] \| Wintech And Chicony [Member] \| Customer concentration risk [Member] \| Minimum [Member]
Concentration Risk [Line Items]
Percentage of revenue or accounts receivable	10.00%	10.00%		10.00%
Sales revenue, net [Member] \| Wintech [Member] \| Customer concentration risk [Member]
Concentration Risk [Line Items]
Percentage of revenue			73.00%
Sales revenue, net [Member] \| Wintech [Member] \| Customer concentration risk [Member] \| Minimum [Member]
Concentration Risk [Line Items]
Percentage of revenue or accounts receivable			10.00%
Accounts receivable [Member] \| Wintech And Chicony [Member] \| Credit concentration risk [Member] \| Minimum [Member]
Concentration Risk [Line Items]
Percentage of revenue or accounts receivable	10.00%	10.00%		10.00%
Accounts receivable [Member] \| Wintech [Member] \| Credit concentration risk [Member] \| Minimum [Member]
Concentration Risk [Line Items]
Percentage of revenue or accounts receivable			10.00%
United States [Member]
Concentration Risk [Line Items]
Property and equipment, net	$ 1,600		$ 1,600
Asia Pacific [Member]
Concentration Risk [Line Items]
Property and equipment, net	$ 1,500		$ 1,500

Segment Reporting - Company's Revenue by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Revenue from External Customer [Line Items]
Total revenue	$ 65,142	$ 84,193	$ 122,299	$ 155,206
Hong Kong [Member]
Revenue from External Customer [Line Items]
Total revenue	56,485	78,628	104,890	144,318
Europe [Member]
Revenue from External Customer [Line Items]
Total revenue	3,282	1,513	8,634	3,703
United States [Member]
Revenue from External Customer [Line Items]
Total revenue	2,327	1,360	4,174	2,566
Asia Pacific [Member]
Revenue from External Customer [Line Items]
Total revenue	1,953	832	3,236	1,316
North America other than United States [Member]
Revenue from External Customer [Line Items]
Total revenue	$ 1,095	$ 1,860	$ 1,365	$ 3,303

Related-Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015	Jan. 31, 2016	Jan. 31, 2013
Related Party Transaction [Line Items]
Percentage of entity's voting stock owned by related party	10.00%		10.00%
Other Entity [Member]
Related Party Transaction [Line Items]
Commitment to make license payment through January 2017			$ 1.6
Payment for license fees	$ 0.7	$ 0.6	1.3	$ 1.4
License expenses included in research and development expense	0.7	0.7	1.4	1.4
Investor [Member]
Related Party Transaction [Line Items]
Percentage of investor own voting stock						4.60%
Recognized revenue from related party	46.8	$ 59.8	88.9	$ 105.1
Account receivables from related party	$ 20.4		$ 20.4		$ 20.6

Financial Instruments and Fair Value - Schedule of Fair Value of Financial Instruments Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 60,623	$ 40,367
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	103	530
Demand deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,000
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	7,479	2,598
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	19,357	21,340
Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	8,452	4,585
U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	13,208	9,272
Agency bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	2,024	2,042
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,103	530
Level 1 [Member] \| Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	103	530
Level 1 [Member] \| Demand deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	10,000
Level 1 [Member] \| Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 1 [Member] \| Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 1 [Member] \| Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 1 [Member] \| U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 1 [Member] \| Agency bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	50,520	39,837
Level 2 [Member] \| Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 2 [Member] \| Demand deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Level 2 [Member] \| Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	7,479	2,598
Level 2 [Member] \| Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	19,357	21,340
Level 2 [Member] \| Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	8,452	4,585
Level 2 [Member] \| U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	13,208	9,272
Level 2 [Member] \| Agency bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	2,024	2,042
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| Demand deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Level 3 [Member] \| Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| U.S. government securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0	0
Level 3 [Member] \| Agency bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 0	$ 0