Ambarella (AMBA) 10-Q 8 Sep 14 2015 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jul. 31, 2014
Document And Entity Information [Abstract]	'
Document Type	'10-Q
Amendment Flag	'false
Document Period End Date	31-Jul-14
Document Fiscal Year Focus	'2015
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	'Accelerated Filer
Entity Common Stock, Shares Outstanding	29,695,783

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (Unaudited) (USD $)	Jul. 31, 2014	Jan. 31, 2014
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$128,263	$143,394
Marketable securities	38,265	'
Accounts receivable, net	26,833	18,837
Inventories	13,003	10,452
Restricted cash	3	3
Deferred tax assets, current	1,599	1,599
Prepaid expenses and other current assets	2,227	2,951
Total current assets	210,193	177,236
Property and equipment, net	3,080	3,018
Deferred tax assets, non-current	1,375	1,134
Other assets	1,772	1,919
Total assets	216,420	183,307
Current liabilities:	'	'
Accounts payable	14,424	8,321
Accrued liabilities	12,344	11,705
Income taxes payable	706	545
Deferred revenue, current	4,888	4,831
Total current liabilities	32,362	25,402
Deferred revenue, non-current	178	'
Other long-term liabilities	1,569	1,544
Total liabilities	34,109	26,946
Commitments and contingencies (Note 11)	'	'
Shareholders' equity:	'	'
Preference shares, $0.00045 par value per share, 20,000,000 shares authorized and no shares issued and outstanding at July 31, 2014 and January 31, 2014, respectively	'	'
Ordinary shares, $0.00045 par value per share, 200,000,000 shares authorized at July 31, 2014 and January 31, 2014, respectively; 29,695,783 shares issued and outstanding at July 31, 2014; 28,748,513 shares issued and outstanding at January 31, 2014	13	13
Additional paid-in capital	121,686	110,285
Accumulated other comprehensive income (loss)	-21	'
Retained earnings	60,633	46,063
Total shareholders' equity	182,311	156,361
Total liabilities and shareholders' equity	$216,420	$183,307

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Jul. 31, 2014	Jan. 31, 2014
Statement Of Financial Position [Abstract]	'	'
Preference shares, par value	$0.00	$0.00
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	$0.00	$0.00
Ordinary shares, shares authorized	200,000,000	200,000,000
Ordinary shares, shares issued	29,695,783	28,748,513
Ordinary shares, shares outstanding	29,695,783	28,748,513

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Income Statement [Abstract]	'	'	'	'
Revenue	$46,968	$37,710	$87,889	$71,651
Cost of revenue	16,432	14,419	31,757	26,667
Gross profit	30,536	23,291	56,132	44,984
Operating expenses:	'	'	'	'
Research and development	13,497	10,974	26,411	22,291
Selling, general and administrative	6,875	5,385	13,630	10,542
Total operating expenses	20,372	16,359	40,041	32,833
Income from operations	10,164	6,932	16,091	12,151
Other income (loss), net	39	-11	88	-16
Income before income taxes	10,203	6,921	16,179	12,135
Provision for income taxes	893	667	1,609	1,140
Net income	$9,310	$6,254	$14,570	$10,995
Net income per share attributable to ordinary shareholders:	'	'	'	'
Basic	$0.32	$0.23	$0.50	$0.40
Diluted	$0.29	$0.21	$0.46	$0.37
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:	'	'	'	'
Basic	29,421,200	27,409,343	29,198,511	27,232,142
Diluted	31,899,501	29,848,676	31,831,489	29,456,374

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]	'	'	'	'
Net income	$9,310	$6,254	$14,570	$10,995
Other comprehensive income (loss):	'	'	'	'
Unrealized gains (losses) on investments	-29	'	-21	'
Other comprehensive income (loss), net of tax	-29	'	-21	'
Comprehensive income	$9,281	$6,254	$14,549	$10,995

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013
Cash flows from operating activities:	'	'
Net income	$14,570	$10,995
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation and amortization of property and equipment	628	481
Amortization/accretion of marketable securities	265	'
Loss on disposal of long-lived assets	4	2
Stock-based compensation	5,823	3,199
Excess income tax benefits associated with stock-based compensation	-416	-267
Other non-cash items, net	-2	'
Changes in operating assets and liabilities:	'	'
Accounts receivable	-7,996	-1,728
Inventories	-2,551	-995
Prepaid expenses and other current assets	973	882
Deferred tax assets	-241	-196
Other assets	147	-14
Accounts payable	6,103	4,388
Accrued liabilities	727	-2,610
Income taxes payable	577	362
Deferred revenue	235	1,440
Net cash provided by operating activities	18,846	15,939
Cash flows from investing activities:	'	'
Purchase of investments	-41,621	'
Sales of investments	10	'
Maturities of investments	2,812	'
Net proceeds from disposal of fixed assets	'	13
Purchase of property and equipment	-678	-1,293
Net cash used in investing activities	-39,477	-1,280
Cash flows from financing activities:	'	'
Proceeds from exercise of stock options, warrants, and employee stock purchase plan withholding, net of repurchase of stock options	5,084	2,915
Payment for initial public offering cost	'	-25
Excess income tax benefits associated with stock-based compensation	416	267
Net cash provided by financing activities	5,500	3,157
Net increase (decrease) in cash and cash equivalents	-15,131	17,816
Cash and cash equivalents at beginning of period	143,394	100,494
Cash and cash equivalents at end of period	128,263	118,310
Supplemental disclosure of cash flow information:	'	'
Cash paid for income taxes	435	314
Supplemental disclosure of noncash investing activities:	'	'
Increase in accrued liabilities related to non-monetary assets purchases	$37	$9

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	6 Months Ended
	Jul. 31, 2014
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 2014 fiscal year filed with the SEC on April 4, 2014 (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 presentation 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 collectability of accounts receivable; (ii) write down for excess and obsolete inventories; (iii) the estimated useful lives of long-lived assets; (iv) impairment of long-lived assets and financial instruments; (v) warranty obligations; (vi) the valuation of stock-based compensation and financial instruments; (vii) the probability of performance objectives achievement; (viii) the realization of tax assets and estimates of tax liabilities, including reserves for uncertain tax positions; and (ix) 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 all of 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 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 12 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, commercial paper and debt securities of corporations which management assesses to be high credit quality, 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, 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 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 has been established and, accordingly, any associated reserve is not reversed until the inventory sold or scrapped. There have been no material inventory losses recognized to date.
	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 right 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 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 sells a limited amount of software under perpetual licenses that include post-contract customer support, or PCS. The Company does not have evidence of fair value for the PCS and, accordingly, license revenue is recognized ratably over the estimated supporting period in accordance with ASC 985, Software Revenue Recognition. The Company also enters into development agreements with certain customers. Revenue is deferred for any amounts billed prior to delivery of development services. However, if the Company retains the intellectual property generated from these development agreements, receipts and costs related to these arrangements are included in research and development expense. The revenue from those licenses and services was not material for the three and six months ended July 31, 2014 and 2013, 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 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 consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the 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 income statement for the periods in which the adjustment is determined to be required.
	Net Income Per Ordinary Share
	The Company applies the two-class method to calculate and present net income per ordinary share. Under the two-class method, net income is allocated between ordinary shares and other participating securities based on their participating rights. Participating securities are defined as securities that may participate in undistributed earnings with ordinary shares, whether that participation is conditioned upon the occurrence of a specified event or not. Basic net income per ordinary share is computed by dividing net income allocable to ordinary shares by the weighted-average number of ordinary shares outstanding for the period. Diluted net income per ordinary share is computed by dividing net income allocable to ordinary shares and income allocable to participating securities, to the extent they are dilutive, by the weighted-average number of ordinary shares outstanding, including the dilutive effects of participating securities plus the dilutive effects of ordinary shares. The Company’s potential dilutive ordinary share equivalents consist of incremental ordinary shares issuable upon the exercise of options, upon the issuance of shares pursuant to the Employee Stock Purchase Plan, or ESPP, and upon release of vested restricted stock units.
	The Company performs an assessment as to whether instruments granted in stock-based payment transactions are participating securities. Stock-based payment awards that have not yet vested meet the definition of a participating security provided the right to receive the dividend is non-forfeitable and non-contingent. These participating securities should be included in the computation of basic net income per ordinary share under the two-class method. The Company has concluded that its non-vested early-exercised options meet the definition of a participating security and should be included in the computation of basic net income per ordinary share.
	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 February 2013, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (“AOCI”). This new guidance requires that the Company present either in a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. If a component is not required to be reclassified to net income in its entirety, the Company would instead cross reference to the related footnote for additional information. This guidance only impacts disclosures within the Company’s consolidated financial statements and notes to the consolidated financial statements and does not result in a change to the accounting treatment of AOCI. This new guidance became effective prospectively for fiscal years, and interim periods with those years, beginning after December 15, 2012. The Company adopted this guidance starting from the first quarter of fiscal year 2014 and the adoption did not have an impact on its financial position, results of operations or disclosures.
	In July 2013, the FASB issued ASU No. 2013-11, Income Taxes (Topic 740), Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss ,or a Tax Credit Carryforward Exists. The new guidance requires the netting of unrecognized tax benefits (“UTBs”) against a deferred tax asset for a loss or other carryforward that would apply in settlement of the uncertain tax positions. Under the new standard, UTBs will be netted against all available same-jurisdiction loss or other tax carryforwards that would be utilized, rather than only against carryforwards that are created by the UTBs. The new guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013 and should be applied prospectively to all unrecognized tax benefits that exist at the effective date. The Company has adopted this new standard on a prospective basis in the first quarter of fiscal year 2015. The implementation had no material impact on its financial position, results of operations, statement of cash flows or disclosures.
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). 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 should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, an entity shall identify the contract(s) with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies a performance obligation. The new guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. Early adoption is not permitted. 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.

Financial_Instruments_and_Fair

Financial Instruments and Fair Value	6 Months Ended
	Jul. 31, 2014
Investments All Other Investments [Abstract]	'
Financial Instruments and Fair Value	'
	2. Financial Instruments and Fair Value
	Beginning in fiscal year 2015, the Company invested a portion of its cash primarily in marketable securities that are denominated in United States dollars. The investment portfolio consists of money market funds, commercial paper 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, 2014
		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
		(in thousands)
	Money market funds	$	319	$	—	$	—		$	319
	Corporate bonds		35,940		7		(28	)		35,919
	Commercial paper		3,548		—		—			3,548
	Total cash equivalents and marketable securities	$	39,807	$	7	$	(28	)	$	39,786
		As of
		July 31, 2014
		(in thousands)
	Included in cash equivalents	$	1,521
	Included in marketable securities		38,265
	Total cash equivalents and marketable securities	$	39,786
	The contractual maturities of the investments at July 31, 2014 were as follows:
		As of
		July 31, 2014
		(in thousands)
	Due within one year	$	31,580
	Due within one to two years		8,206
	Total cash equivalents and marketable securities	$	39,786
	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 will 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, 2014.
	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 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 asserts 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, 2014:
		Total		Level 1		Level 2			Level 3
		(in thousands)
	Money market funds	$	319	$	319	$	—		$	—
	Corporate bonds		35,919		—		35,919			—
	Commercial paper		3,548		—		3,548			—
	Total cash equivalents and marketable securities	$	39,786	$	319	$	39,467		$	—

Inventories

Inventories	6 Months Ended
	Jul. 31, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	3. Inventories
	Inventory at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014		January 31, 2014
		(in thousands)
	Work-in-progress	$	9,096	$	5,119
	Finished goods		3,907		5,333
	Total	$	13,003	$	10,452

Property_and_Equipment_Net

Property and Equipment, Net	6 Months Ended
	Jul. 31, 2014
Property Plant And Equipment [Abstract]	'
Property and Equipment, Net	'
	4. Property and Equipment, Net
	Depreciation and amortization expense was approximately $0.3 million for the three months ended July 31, 2014 and 2013, respectively. Depreciation and amortization expense was approximately $0.6 million and $0.5 million for the six months ended July 31, 2014 and 2013, respectively. Property and equipment at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014			January 31, 2014
		(in thousands)
	Computer equipment and software	$	5,079		$	4,521
	Machinery and equipment		2,153			2,114
	Furniture and fixtures		450			411
	Leasehold improvements		1,189			1,198
			8,871			8,244
	Less: accumulated depreciation and amortization		(5,791	)		(5,226	)
	Total property and equipment, net	$	3,080		$	3,018

Accrued_Liabilities

Accrued Liabilities	6 Months Ended
	Jul. 31, 2014
Payables And Accruals [Abstract]	'
Accrued Liabilities	'
	5. Accrued Liabilities
	Accrued liabilities at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014		January 31, 2014
		(in thousands)
	Accrued employee compensation	$	7,375	$	8,108
	Accrued warranty		234		269
	Accrued rebates		440		270
	Accrued product development costs		2,833		1,904
	Other accrued liabilities		1,462		1,154
	Total accrued liabilities	$	12,344	$	11,705

Deferred_Revenue_and_Deferred_

Deferred Revenue and Deferred Cost	6 Months Ended
	Jul. 31, 2014
Deferred Revenue Disclosure [Abstract]	'
Deferred Revenue and Deferred Cost	'
	6. Deferred Revenue and Deferred Cost
	Deferred revenue and related cost at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014			January 31, 2014
		(in thousands)
	Deferred revenue on product shipments	$	5,523		$	5,174
	Deferred revenue from licenses & services		1,007			1,023
	Deferred cost of revenue on product shipments		(1,464	)		(1,366	)
	Total deferred revenue, net	$	5,066		$	4,831

Capital_Stock

Capital Stock	6 Months Ended
	Jul. 31, 2014
Text Block [Abstract]	'
Capital Stock	'
	7. 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, 2014 and January 31, 2014, respectively.
	Ordinary shares
	At July 31, 2014 and January 31, 2014, a total of 200,000,000 ordinary shares were authorized.
	On February 1, 2014, the Company added 1,297,555 ordinary shares to the ordinary shares reserved for issuance under the 2012 Equity Incentive Plan, or EIP, pursuant to an “evergreen” provision contained in the 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, 2014, the Company added 359,356 ordinary shares to the ordinary shares reserved for issuance under the 2012 Employee Stock Purchase Plan, or ESPP, pursuant to an “evergreen” provision contained in the 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, 2014 and January 31, 2014, the following ordinary shares were reserved for future issuance under the EIP and ESPP:
		As of
		July 31, 2014		January 31, 2014
	Shares reserved for options and restricted stock units		6,140,955		5,699,530
	Shares reserved for employee stock purchase plan		724,626		456,410

Stockbased_Compensation

Stock-based Compensation	6 Months Ended
	Jul. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-based Compensation	'
	8. 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,
		2014			2013			2014			2013
		(in thousands)
	Stock-based compensation:
	Cost of revenue	$	58		$	34		$	117		$	68
	Research and development		1,629			900			3,219			1,874
	Selling, general and administrative		1,262			659			2,487			1,257
	Total stock-based compensation	$	2,949		$	1,593		$	5,823		$	3,199
	As of July 31, 2014, total unrecognized compensation cost related to unvested stock options and unvested restricted stock units was $6.2 million and $15.6 million, respectively, and is expected to be recognized over a weighted-average period of 2.09 years and 2.64 years, respectively. As of January 31, 2014, total unrecognized compensation cost related to unvested stock options and unvested restricted stock units was $5.8 million and $17.0 million, respectively, and is expected to be recognized over a weighted-average period of 1.90 years and 2.99 years, respectively.
	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,
		2014			2013			2014			2013
	Stock Options:
	Volatility		64	%		66	%		65	%		65	%
	Risk-free interest rate		1.9	%		1.25	%		1.93	%		1.21	%
	Expected term (years)		6.08			6.05			6.06			6.05
	Dividend yield		0	%		0	%		0	%		0	%
	Employee stock purchase plan awards:
	Volatility		—			—			57	%		—
	Risk-free interest rate		—			—			0.08	%		—
	Expected term (years)		—			—			0.5			—
	Dividend yield		—			—			0	%		—
	The following table summarizes stock option activities for the six months ended July 31, 2014:
		Option Outstanding
		Shares			Weighted-			Weighted-			Total Intrinsic			Weighted-		Aggregate
					Average			Average			Value of			Average		Intrinsic Value
					Exercise Price			Grant-date			options			Remaining		(in thousands)
								Fair Value			Exercised			Contactual
											(in thousands)			Term
														(in years)
	Outstanding at January 31, 2014		3,358,706		$	6.92
	Granted		151,333			29.26		$	17.51
	Exercised		(653,486	)		5.72					$	15,623
	Forfeited		(31,916	)		11.38
	Outstanding at July 31, 2014		2,824,637			8.35									6.1	$	57,493
	Exercisable at July 31, 2014		2,138,115			6.03									5.43	$	48,281
	Vested and expected to vest at July 31, 2014		2,783,352			8.2									6.07	$	57,051
	Exercisable shares include options with early exercise rights. The vested and expected-to-vest options are calculated based on the vesting schedule of each grant as of the reporting date.
	The intrinsic value of options outstanding, exercisable 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 $28.61 on July 31, 2014, 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 unit activities for the six months ended July 31, 2014:
		Shares			Weighted-
					Average
					Grant-Date
					Fair Value
	Unvested at January 31, 2014		1,410,089		$	14.02
	Granted		73,667			29.93
	Vested		(202,644	)		13.89
	Forfeited		(25,902	)		13.46
	Unvested at July 31, 2014		1,255,210		$	14.99
	As of July 31, 2014, the aggregate intrinsic value of unvested restricted stock units was $35.9 million.
	Non-employee Stock-based Compensation
	The fair value of awards granted to non-employees is determined on the grant date and remeasured at the end of each reporting period until such awards vest. The non-employee stock-based compensation expense was not material for the three and six months ended July 31, 2014 and 2013, respectively.

Net_Income_Per_Ordinary_Share

Net Income Per Ordinary Share	6 Months Ended
	Jul. 31, 2014
Earnings Per Share [Abstract]	'
Net Income Per Ordinary Share	'
	9. 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,
		2014			2013			2014			2013
		(in thousands, except share and per share data)
	Numerator:
	Net income	$	9,310		$	6,254		$	14,570		$	10,995
	Less: amount allocable to unvested early exercised options		(2	)		(8	)		(4	)		(17	)
	Net income allocable to ordinary shareholders - basic	$	9,308		$	6,246		$	14,566		$	10,978
	Undistributed earnings reallocated to ordinary shareholders		—			1			—			1
	Net income allocable to ordinary shareholders - diluted	$	9,308		$	6,247		$	14,566		$	10,979
	Denominator:
	Weighted-average ordinary shares outstanding		29,426,935			27,443,622			29,206,936			27,273,376
	Less: weighted-average unvested early exercised options subject to repurchase		(5,735	)		(34,279	)		(8,425	)		(41,234	)
	Weighted-average ordinary shares - basic		29,421,200			27,409,343			29,198,511			27,232,142
	Effect of potentially dilutive securities:
	Employee stock options		1,879,067			2,046,623			1,994,912			1,867,695
	Restricted stock units		599,234			159,434			627,368			150,541
	Employee stock purchase plan		—			231,278			10,698			201,048
	Warrants to purchase ordinary shares		—			1,998			—			4,948
	Weighted-average ordinary shares - diluted		31,899,501			29,848,676			31,831,489			29,456,374
	Net income per ordinary share:
	Basic	$	0.32		$	0.23		$	0.5		$	0.4
	Diluted	$	0.29		$	0.21		$	0.46		$	0.37
	Earnings per share (EPS) of ordinary shares is calculated using the two-class method required for participating securities. Net income has been allocated to the ordinary shares and participating securities based on their respective rights to share in net income and weighted-average outstanding during the periods.
	The following weighted-average potentially dilutive securities are 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,
		2014			2013			2014			2013
	Options to purchase ordinary shares		193,633			102,707			156,550			246,817
	Restricted stock units		52,978			—			42,167			3,151
	Employee stock purchase plan		62,887			—			47,165			—
	Early exercised options subject to repurchase		5,735			34,279			8,425			41,234
			315,233			136,986			254,307			291,202

Income_Taxes

Income Taxes	6 Months Ended
	Jul. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	10. Income Taxes
	The Company reported the following income tax for the periods indicated:
		Three Months Ended July 31,				Six Months Ended July 31,
		2014		2013		2014		2013
		(in thousands)
	Income tax expense	$	893	$	667	$	1,609	$	1,140
	The effective tax rate was 8.8% and 9.6% for the three months ended July 31, 2014 and 2013, respectively. The effective tax rate was 9.9% and 9.4% for the six months ended July 31, 2014 and 2013, respectively. The decrease in the tax rate for the three months ended July 31, 2014 compared to the three months ended July 31, 2013 was primarily due to a change in the mix of earnings of various geographic jurisdictions between the two periods. The increase in the tax rate for the six months ended July 31, 2014 compared to the six months ended July 31, 2013 was primarily due to the expiration of the US federal R&D tax credit on December 31, 2013, and the changes in the mix of earnings of various geographic jurisdictions in the fiscal year 2015 as compared to the fiscal year 2014. The quarterly income taxes reflect an estimation of the corresponding fiscal year’s annual effective tax rate and include, when applicable, adjustments from discrete tax items.
	The Company files federal and state income tax returns in the United States and in various foreign jurisdictions. The tax years 2007 to 2009 and 2011 to 2013 remain open to examination by U.S. federal tax authorities. The tax years 2004 to 2013 remain open to examination by U.S. state tax authorities. The tax years 2010 to 2013 remain open to examination by material foreign tax authorities.
	The Company is subject to ongoing tax 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, 2014, the gross amount of unrecognized tax benefits was approximately $3.6 million. If the estimates of income tax liabilities prove to be less than the ultimate assessment, then a further charge to expense would be required. If events occur and the payment of these amounts ultimately proves to be unnecessary, the reversal of the liabilities would 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 any material changes to its uncertain tax positions during the next twelve months.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jul. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	11. Commitments and Contingencies
	The Company leases its principal facilities and time-based software licenses under operating agreements with various expiration dates through April 2018. Net operating lease expenses for the three months ended July 31, 2014 and 2013 were approximately $1.5 million and $1.3 million, respectively. Net operating lease expenses for the six months ended July 31, 2014 and 2013 were approximately $2.8 million and $2.4 million, respectively. Future annual minimum lease payments under these operating leases with initial lease terms in excess of one year are as follows:
		As of
		July 31, 2014
	Fiscal Year	(in thousands)
	2015		2,687
	2016		5,079
	2017		4,622
	2018		1,381
	2019		238
	Total future annual minimum lease payments	$	14,007
	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. As of July 31, 2014 and January 31, 2014, total manufacturing purchase commitments were approximately $18.4 million and $13.7 million, respectively.
	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, 2014 and January 31, 2014, respectively.

Segment_Reporting

Segment Reporting	6 Months Ended
	Jul. 31, 2014
Segment Reporting [Abstract]	'
Segment Reporting	'
	12. 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 of 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,
		2014		2013		2014		2013
		(in thousands)
	Hong Kong	$	41,999	$	33,195	$	77,393	$	61,969
	Asia Pacific		585		446		1,218		702
	United States		1,721		1,242		3,868		3,847
	North America		1,445		1,071		2,716		2,033
	Europe		1,218		1,756		2,694		3,100
	Total revenue	$	46,968	$	37,710	$	87,889	$	71,651
	As of July 31, 2014, substantially all of the Company’s long-lived tangible assets were located in the Asia Pacific region.
	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 88% and 87% of total revenue for the three months ended July 31, 2014 and 2013, respectively, and approximately 87% and 84% of total revenue for the six months ended July 31, 2014 and 2013, respectively. Accounts receivable with these two customers combined accounted for approximately $23.6 million and $15.9 million as of July 31, 2014 and January 31, 2014, respectively.

RelatedParty_Transactions

Related-Party Transactions	6 Months Ended
	Jul. 31, 2014
Related Party Transactions [Abstract]	'
Related-Party Transactions	'
	13. 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.
	In April 2014, the Company added additional software license commitments to its existing software license agreement 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. Under these license commitments, the Company committed to pay an aggregate amount of $6.9 million payable through January 2017. The Company paid $0.6 million and $0.4 million of license fees to Cadence for the three months ended July 31, 2014 and 2013, respectively. The Company paid $1.0 million and $0.9 million of license fees to Cadence for the six months ended July 31, 2014 and 2013, respectively. Operating lease expenses related to these commitments included in research and development cost were approximately $0.5 million and $0.4 million for the three months ended July 31, 2014 and 2013, respectively. Operating lease expenses related to these commitments included in research and development cost were approximately $0.7 million and $0.9 million for the six months ended July 31, 2014 and 2013, respectively.
	In addition to the related party transactions noted above, the Company recognized revenue from sales to Wintech Microelectronics Co., Ltd, or 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 January 31, 2014. The Company recognized revenue from sales to Wintech of approximately $30.3 million and $22.1 million for the three months ended July 31, 2014 and 2013, respectively. The Company recognized revenue from sales to Wintech of approximately $58.5 million and $35.5 million for the six months ended July 31, 2014 and 2013, respectively. As of July 31, 2014 and January 31, 2014, the Company had receivables from Wintech of approximately $12.5 million and $7.9 million, respectively.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jul. 31, 2014
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 2014 fiscal year filed with the SEC on April 4, 2014 (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 presentation 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 collectability of accounts receivable; (ii) write down for excess and obsolete inventories; (iii) the estimated useful lives of long-lived assets; (iv) impairment of long-lived assets and financial instruments; (v) warranty obligations; (vi) the valuation of stock-based compensation and financial instruments; (vii) the probability of performance objectives achievement; (viii) the realization of tax assets and estimates of tax liabilities, including reserves for uncertain tax positions; and (ix) 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 all of 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 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 12 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, commercial paper and debt securities of corporations which management assesses to be high credit quality, 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, Cash Equivalents and Marketable Securities	'
	Cash, 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 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 has been established and, accordingly, any associated reserve is not reversed until the inventory sold or scrapped. There have been no material inventory losses recognized to date.
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 right 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 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 sells a limited amount of software under perpetual licenses that include post-contract customer support, or PCS. The Company does not have evidence of fair value for the PCS and, accordingly, license revenue is recognized ratably over the estimated supporting period in accordance with ASC 985, Software Revenue Recognition. The Company also enters into development agreements with certain customers. Revenue is deferred for any amounts billed prior to delivery of development services. However, if the Company retains the intellectual property generated from these development agreements, receipts and costs related to these arrangements are included in research and development expense. The revenue from those licenses and services was not material for the three and six months ended July 31, 2014 and 2013, 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 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 consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the 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 income statement for the periods in which the adjustment is determined to be required.
Net Income Per Ordinary Share	'
	Net Income Per Ordinary Share
	The Company applies the two-class method to calculate and present net income per ordinary share. Under the two-class method, net income is allocated between ordinary shares and other participating securities based on their participating rights. Participating securities are defined as securities that may participate in undistributed earnings with ordinary shares, whether that participation is conditioned upon the occurrence of a specified event or not. Basic net income per ordinary share is computed by dividing net income allocable to ordinary shares by the weighted-average number of ordinary shares outstanding for the period. Diluted net income per ordinary share is computed by dividing net income allocable to ordinary shares and income allocable to participating securities, to the extent they are dilutive, by the weighted-average number of ordinary shares outstanding, including the dilutive effects of participating securities plus the dilutive effects of ordinary shares. The Company’s potential dilutive ordinary share equivalents consist of incremental ordinary shares issuable upon the exercise of options, upon the issuance of shares pursuant to the Employee Stock Purchase Plan, or ESPP, and upon release of vested restricted stock units.
	The Company performs an assessment as to whether instruments granted in stock-based payment transactions are participating securities. Stock-based payment awards that have not yet vested meet the definition of a participating security provided the right to receive the dividend is non-forfeitable and non-contingent. These participating securities should be included in the computation of basic net income per ordinary share under the two-class method. The Company has concluded that its non-vested early-exercised options meet the definition of a participating security and should be included in the computation of basic net income per ordinary share.
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 February 2013, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (“AOCI”). This new guidance requires that the Company present either in a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income based on its source and the income statement line items affected by the reclassification. If a component is not required to be reclassified to net income in its entirety, the Company would instead cross reference to the related footnote for additional information. This guidance only impacts disclosures within the Company’s consolidated financial statements and notes to the consolidated financial statements and does not result in a change to the accounting treatment of AOCI. This new guidance became effective prospectively for fiscal years, and interim periods with those years, beginning after December 15, 2012. The Company adopted this guidance starting from the first quarter of fiscal year 2014 and the adoption did not have an impact on its financial position, results of operations or disclosures.
	In July 2013, the FASB issued ASU No. 2013-11, Income Taxes (Topic 740), Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss ,or a Tax Credit Carryforward Exists. The new guidance requires the netting of unrecognized tax benefits (“UTBs”) against a deferred tax asset for a loss or other carryforward that would apply in settlement of the uncertain tax positions. Under the new standard, UTBs will be netted against all available same-jurisdiction loss or other tax carryforwards that would be utilized, rather than only against carryforwards that are created by the UTBs. The new guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013 and should be applied prospectively to all unrecognized tax benefits that exist at the effective date. The Company has adopted this new standard on a prospective basis in the first quarter of fiscal year 2015. The implementation had no material impact on its financial position, results of operations, statement of cash flows or disclosures.
	In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). 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 should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, an entity shall identify the contract(s) with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies a performance obligation. The new guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. Early adoption is not permitted. 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.

Financial_Instruments_and_Fair1

Financial Instruments and Fair Value (Tables)	6 Months Ended
	Jul. 31, 2014
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, 2014
		Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
		(in thousands)
	Money market funds	$	319	$	—	$	—		$	319
	Corporate bonds		35,940		7		(28	)		35,919
	Commercial paper		3,548		—		—			3,548
	Total cash equivalents and marketable securities	$	39,807	$	7	$	(28	)	$	39,786
Schedule of Cash Equivalents and Marketable Securities	'
		As of
		July 31, 2014
		(in thousands)
	Included in cash equivalents	$	1,521
	Included in marketable securities		38,265
	Total cash equivalents and marketable securities	$	39,786
Summary of Contractual Maturities of Investments	'
	The contractual maturities of the investments at July 31, 2014 were as follows:
		As of
		July 31, 2014
		(in thousands)
	Due within one year	$	31,580
	Due within one to two years		8,206
	Total cash equivalents and marketable securities	$	39,786
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, 2014:
		Total		Level 1		Level 2			Level 3
		(in thousands)
	Money market funds	$	319	$	319	$	—		$	—
	Corporate bonds		35,919		—		35,919			—
	Commercial paper		3,548		—		3,548			—
	Total cash equivalents and marketable securities	$	39,786	$	319	$	39,467		$	—

Inventories_Tables

Inventories (Tables)	6 Months Ended
	Jul. 31, 2014
Inventory Disclosure [Abstract]	'
Schedule of Inventory	'
	Inventory at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014		January 31, 2014
		(in thousands)
	Work-in-progress	$	9,096	$	5,119
	Finished goods		3,907		5,333
	Total	$	13,003	$	10,452

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	6 Months Ended
	Jul. 31, 2014
Property Plant And Equipment [Abstract]	'
Schedule of Property and Equipment	'
	Property and equipment at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014			January 31, 2014
		(in thousands)
	Computer equipment and software	$	5,079		$	4,521
	Machinery and equipment		2,153			2,114
	Furniture and fixtures		450			411
	Leasehold improvements		1,189			1,198
			8,871			8,244
	Less: accumulated depreciation and amortization		(5,791	)		(5,226	)
	Total property and equipment, net	$	3,080		$	3,018

Accrued_Liabilities_Tables

Accrued Liabilities (Tables)	6 Months Ended
	Jul. 31, 2014
Payables And Accruals [Abstract]	'
Schedule of Accrued Liabilities	'
	Accrued liabilities at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014		January 31, 2014
		(in thousands)
	Accrued employee compensation	$	7,375	$	8,108
	Accrued warranty		234		269
	Accrued rebates		440		270
	Accrued product development costs		2,833		1,904
	Other accrued liabilities		1,462		1,154
	Total accrued liabilities	$	12,344	$	11,705

Deferred_Revenue_and_Deferred_1

Deferred Revenue and Deferred Cost (Tables)	6 Months Ended
	Jul. 31, 2014
Deferred Revenue Disclosure [Abstract]	'
Schedule of Deferred Revenue and Related Cost	'
	Deferred revenue and related cost at July 31, 2014 and January 31, 2014 consisted of the following:
		As of
		July 31, 2014			January 31, 2014
		(in thousands)
	Deferred revenue on product shipments	$	5,523		$	5,174
	Deferred revenue from licenses & services		1,007			1,023
	Deferred cost of revenue on product shipments		(1,464	)		(1,366	)
	Total deferred revenue, net	$	5,066		$	4,831

Capital_Stock_Tables

Capital Stock (Tables)	6 Months Ended
	Jul. 31, 2014
Text Block [Abstract]	'
Schedule of Ordinary Shares Reserved for Future Issuance under EIP and ESPP	'
	As of July 31, 2014 and January 31, 2014, the following ordinary shares were reserved for future issuance under the EIP and ESPP:
		As of
		July 31, 2014		January 31, 2014
	Shares reserved for options and restricted stock units		6,140,955		5,699,530
	Shares reserved for employee stock purchase plan		724,626		456,410

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	6 Months Ended
	Jul. 31, 2014
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,
		2014			2013			2014			2013
		(in thousands)
	Stock-based compensation:
	Cost of revenue	$	58		$	34		$	117		$	68
	Research and development		1,629			900			3,219			1,874
	Selling, general and administrative		1,262			659			2,487			1,257
	Total stock-based compensation	$	2,949		$	1,593		$	5,823		$	3,199
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,
		2014			2013			2014			2013
	Stock Options:
	Volatility		64	%		66	%		65	%		65	%
	Risk-free interest rate		1.9	%		1.25	%		1.93	%		1.21	%
	Expected term (years)		6.08			6.05			6.06			6.05
	Dividend yield		0	%		0	%		0	%		0	%
	Employee stock purchase plan awards:
	Volatility		—			—			57	%		—
	Risk-free interest rate		—			—			0.08	%		—
	Expected term (years)		—			—			0.5			—
	Dividend yield		—			—			0	%		—
Stock Option Activities	'
	The following table summarizes stock option activities for the six months ended July 31, 2014:
		Option Outstanding
		Shares			Weighted-			Weighted-			Total Intrinsic			Weighted-		Aggregate
					Average			Average			Value of			Average		Intrinsic Value
					Exercise Price			Grant-date			options			Remaining		(in thousands)
								Fair Value			Exercised			Contactual
											(in thousands)			Term
														(in years)
	Outstanding at January 31, 2014		3,358,706		$	6.92
	Granted		151,333			29.26		$	17.51
	Exercised		(653,486	)		5.72					$	15,623
	Forfeited		(31,916	)		11.38
	Outstanding at July 31, 2014		2,824,637			8.35									6.1	$	57,493
	Exercisable at July 31, 2014		2,138,115			6.03									5.43	$	48,281
	Vested and expected to vest at July 31, 2014		2,783,352			8.2									6.07	$	57,051
Restricted Stock Unit Activities	'
	The following table summarizes restricted stock unit activities for the six months ended July 31, 2014:
		Shares			Weighted-
					Average
					Grant-Date
					Fair Value
	Unvested at January 31, 2014		1,410,089		$	14.02
	Granted		73,667			29.93
	Vested		(202,644	)		13.89
	Forfeited		(25,902	)		13.46
	Unvested at July 31, 2014		1,255,210		$	14.99

Net_Income_Per_Ordinary_Share_

Net Income Per Ordinary Share (Tables)	6 Months Ended
	Jul. 31, 2014
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,
		2014			2013			2014			2013
		(in thousands, except share and per share data)
	Numerator:
	Net income	$	9,310		$	6,254		$	14,570		$	10,995
	Less: amount allocable to unvested early exercised options		(2	)		(8	)		(4	)		(17	)
	Net income allocable to ordinary shareholders - basic	$	9,308		$	6,246		$	14,566		$	10,978
	Undistributed earnings reallocated to ordinary shareholders		—			1			—			1
	Net income allocable to ordinary shareholders - diluted	$	9,308		$	6,247		$	14,566		$	10,979
	Denominator:
	Weighted-average ordinary shares outstanding		29,426,935			27,443,622			29,206,936			27,273,376
	Less: weighted-average unvested early exercised options subject to repurchase		(5,735	)		(34,279	)		(8,425	)		(41,234	)
	Weighted-average ordinary shares - basic		29,421,200			27,409,343			29,198,511			27,232,142
	Effect of potentially dilutive securities:
	Employee stock options		1,879,067			2,046,623			1,994,912			1,867,695
	Restricted stock units		599,234			159,434			627,368			150,541
	Employee stock purchase plan		—			231,278			10,698			201,048
	Warrants to purchase ordinary shares		—			1,998			—			4,948
	Weighted-average ordinary shares - diluted		31,899,501			29,848,676			31,831,489			29,456,374
	Net income per ordinary share:
	Basic	$	0.32		$	0.23		$	0.5		$	0.4
	Diluted	$	0.29		$	0.21		$	0.46		$	0.37
Weighted-Average Potentially Dilutive Securities Excluded from Computation of Diluted Net Income Per Ordinary Share	'
	The following weighted-average potentially dilutive securities are 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,
		2014			2013			2014			2013
	Options to purchase ordinary shares		193,633			102,707			156,550			246,817
	Restricted stock units		52,978			—			42,167			3,151
	Employee stock purchase plan		62,887			—			47,165			—
	Early exercised options subject to repurchase		5,735			34,279			8,425			41,234
			315,233			136,986			254,307			291,202

Income_Taxes_Tables

Income Taxes (Tables)	6 Months Ended
	Jul. 31, 2014
Income Tax Disclosure [Abstract]	'
Summary of Reported Income Tax	'
	The Company reported the following income tax for the periods indicated:
		Three Months Ended July 31,				Six Months Ended July 31,
		2014		2013		2014		2013
		(in thousands)
	Income tax expense	$	893	$	667	$	1,609	$	1,140

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	6 Months Ended
	Jul. 31, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Future Annual Minimum Lease Payments	'
	Future annual minimum lease payments under these operating leases with initial lease terms in excess of one year are as follows:
		As of
		July 31, 2014
	Fiscal Year	(in thousands)
	2015		2,687
	2016		5,079
	2017		4,622
	2018		1,381
	2019		238
	Total future annual minimum lease payments	$	14,007

Segment_Reporting_Tables

Segment Reporting (Tables)	6 Months Ended
	Jul. 31, 2014
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,
		2014		2013		2014		2013
		(in thousands)
	Hong Kong	$	41,999	$	33,195	$	77,393	$	61,969
	Asia Pacific		585		446		1,218		702
	United States		1,721		1,242		3,868		3,847
	North America		1,445		1,071		2,716		2,033
	Europe		1,218		1,756		2,694		3,100
	Total revenue	$	46,968	$	37,710	$	87,889	$	71,651

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jul. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Cash equivalents, treatment	'Highly liquid investments with original maturities of less than three months at the time of purchase to be cash equivalents.
Marketable securities, treatment	'Investments that are highly liquid with original maturities at the time of purchase greater than three months are considered as marketable securities.

Financial_Instruments_and_Fair2

Financial Instruments and Fair Value - Schedule of Available-for-Sale Securities at Fair Value (Detail) (USD $)	Jul. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'
Amortized Cost	$39,807
Unrealized Gains	7
Unrealized Losses	-28
Fair Value	39,786
Money market funds [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Amortized Cost	319
Unrealized Gains	'
Unrealized Losses	'
Fair Value	319
Corporate bonds [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Amortized Cost	35,940
Unrealized Gains	7
Unrealized Losses	-28
Fair Value	35,919
Commercial paper [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Amortized Cost	3,548
Unrealized Gains	'
Unrealized Losses	'
Fair Value	$3,548

Financial_Instruments_and_Fair3

Financial Instruments and Fair Value - Schedule of Cash Equivalents and Marketable Securities (Detail) (USD $)	Jul. 31, 2014
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'
Total cash equivalents and marketable securities	$39,786
Included in cash equivalents [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total cash equivalents and marketable securities	1,521
Included in marketable securities [Member]	'
Schedule of Available-for-sale Securities [Line Items]	'
Total cash equivalents and marketable securities	$38,265

Financial_Instruments_and_Fair4

Financial Instruments and Fair Value - Summary of Contractual Maturities of Investments (Detail) (USD $)	Jul. 31, 2014
In Thousands, unless otherwise specified
Available For Sale Securities Debt Maturities Fair Value [Abstract]	'
Due within one year	$31,580
Due within one to two years	8,206
Total cash equivalents and marketable securities	$39,786

Financial_Instruments_and_Fair5

Financial Instruments and Fair Value - Schedule of Fair Value of Financial Instruments Measured on Recurring Basis (Detail) (USD $)	Jul. 31, 2014
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	$39,786
Money market funds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	319
Corporate bonds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	35,919
Commercial paper [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	3,548
Level 1 [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	319
Level 1 [Member] | Money market funds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	319
Level 1 [Member] | Corporate bonds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 1 [Member] | Commercial paper [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 2 [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	39,467
Level 2 [Member] | Money market funds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 2 [Member] | Corporate bonds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	35,919
Level 2 [Member] | Commercial paper [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	3,548
Level 3 [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 3 [Member] | Money market funds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 3 [Member] | Corporate bonds [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'
Level 3 [Member] | Commercial paper [Member]	'
Schedule Of Available For Sale Securities Fair Value Hierarchy [Line Items]	'
Total cash equivalents and marketable securities	'

Inventories_Schedule_of_Invent

Inventories - Schedule of Inventory (Detail) (USD $)	Jul. 31, 2014	Jan. 31, 2014
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Work-in-progress	$9,096	$5,119
Finished goods	3,907	5,333
Total	$13,003	$10,452

Property_and_Equipment_Net_Add

Property and Equipment, Net - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Property Plant And Equipment [Abstract]	'	'	'	'
Depreciation and amortization expense	$0.30	$0.30	$0.60	$0.50

Property_and_Equipment_Net_Sch

Property and Equipment, Net - Schedule of Property and Equipment (Detail) (USD $)	Jul. 31, 2014	Jan. 31, 2014
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	$8,871	$8,244
Less: accumulated depreciation and amortization	-5,791	-5,226
Total property and equipment, net	3,080	3,018
Computer equipment and software [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	5,079	4,521
Machinery and equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	2,153	2,114
Furniture and fixtures [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	450	411
Leasehold improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property and equipment, gross	$1,189	$1,198

Accrued_Liabilities_Schedule_o

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) (USD $)	Jul. 31, 2014	Jan. 31, 2014
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]	'	'
Accrued employee compensation	$7,375	$8,108
Accrued warranty	234	269
Accrued rebates	440	270
Accrued product development costs	2,833	1,904
Other accrued liabilities	1,462	1,154
Total accrued liabilities	$12,344	$11,705

Deferred_Revenue_and_Deferred_2

Deferred Revenue and Deferred Cost - Schedule of Deferred Revenue and Related Cost (Detail) (USD $)	Jul. 31, 2014	Jan. 31, 2014
In Thousands, unless otherwise specified
Deferred Revenue Arrangement [Line Items]	'	'
Deferred cost of revenue on product shipments	($1,464)	($1,366)
Deferred revenue	5,066	4,831
Product shipments [Member]	'	'
Deferred Revenue Arrangement [Line Items]	'	'
Deferred revenue	5,523	5,174
License and services [Member]	'	'
Deferred Revenue Arrangement [Line Items]	'	'
Deferred revenue	$1,007	$1,023

Capital_Stock_Additional_Infor

Capital Stock - Additional Information (Detail) (USD $)	Jul. 31, 2014	Jan. 31, 2014	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2014	Jul. 31, 2014
			2012 Equity Incentive Plan [Member]	2012 Equity Incentive Plan [Member]	2012 Employee Stock Purchase Plan [Member]	2012 Employee Stock Purchase Plan [Member]
				Scenario, plan automatically increased by the lessor of [Member]		Scenario, plan automatically increased by the lessor of [Member]
Class of Stock [Line Items]	'	'	'	'	'	'
Preference shares, shares authorized	20,000,000	20,000,000	'	'	'	'
Preference shares, par value	$0.00	$0.00	'	'	'	'
Preference shares, shares issued	0	0	'	'	'	'
Preference shares, shares outstanding	0	0	'	'	'	'
Ordinary shares authorized	200,000,000	200,000,000	'	'	'	'
Additional ordinary shares reserved for issuance	'	'	1,297,555	'	359,356	'
Annual increase in ordinary shares for available for future issuance	'	'	'	3,500,000	'	1,500,000
Annual shares increase for future issuance by percentage under 2012 equity plan	'	'	'	4.50%	'	'
Annual shares increase for future issuance by percentage under 2012 employee stock purchase plan	'	'	'	'	'	1.25%

Capital_Stock_Schedule_of_Ordi

Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance under EIP and ESPP (Detail)	Jul. 31, 2014	Jan. 31, 2014
Equity Incentive Plan [Member]	'	'
Class of Stock [Line Items]	'	'
Shares reserved	6,140,955	5,699,530
Employee stock purchase plan awards [Member]	'	'
Class of Stock [Line Items]	'	'
Shares reserved	724,626	456,410

Stockbased_Compensation_Classi

Stock-based Compensation - Classification of Stock-based Compensation (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Stock-based compensation:	'	'	'	'
Total stock-based compensation	$2,949	$1,593	$5,823	$3,199
Cost of revenue [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	58	34	117	68
Research and development [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	1,629	900	3,219	1,874
Selling, general and administrative [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	$1,262	$659	$2,487	$1,257

Stockbased_Compensation_Additi

Stock-based Compensation - Additional Information (Detail) (USD $)	6 Months Ended	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jul. 31, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Closing price of ordinary shares	$28.61	'
Unvested stock options [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Total unrecognized compensation cost, stock options	$6.20	$5.80
Weighted-average period	'2 years 1 month 2 days	'1 year 10 months 24 days
Unvested restricted stock units [Member]	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Total unrecognized compensation cost, restricted stock units	15.6	17
Weighted-average period	'2 years 7 months 21 days	'2 years 11 months 27 days
Aggregate intrinsic value of unvested restricted stock units	$35.90	'

Stockbased_Compensation_Weight

Stock-based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value (Detail)	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Options to purchase ordinary shares [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Volatility	64.00%	66.00%	65.00%	65.00%
Risk-free interest rate	1.90%	1.25%	1.93%	1.21%
Expected term (years)	'6 years 29 days	'6 years 18 days	'6 years 22 days	'6 years 18 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	'	'	57.00%	'
Risk-free interest rate	'	'	0.08%	'
Expected term (years)	'	'	'6 months	'
Dividend yield	'	'	0.00%	'

Stockbased_Compensation_Stock_

Stock-based Compensation - Stock Option Activities (Detail) (USD $)	6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jul. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Shares, Outstanding	3,358,706
Shares, Granted	151,333
Shares, Exercised	-653,486
Shares, Forfeited	-31,916
Shares, Outstanding	2,824,637
Shares, Exercisable	2,138,115
Shares, Vested and expected to vest	2,783,352
Weighted-Average Exercise Price, Outstanding	$6.92
Weighted-Average Exercise Price, Granted	$29.26
Weighted-Average Exercise Price, Exercised	$5.72
Weighted-Average Exercise Price, Forfeited	$11.38
Weighted-Average Exercise Price, Outstanding	$8.35
Weighted-Average Exercise Price, Exercisable	$6.03
Weighted-Average Exercise Price, Vested and expected to vest	$8.20
Weighted-Average Grant-date Fair Value, Granted	$17.51
Total Intrinsic Value of options Exercised, Exercised	$15,623
Weighted-Average Remaining Contractual Term, Outstanding	'6 years 1 month 6 days
Weighted-Average Remaining Contractual Term, Exercisable	'5 years 5 months 5 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	'6 years 26 days
Aggregate Intrinsic Value, Outstanding	57,493
Aggregate Intrinsic Value, Exercisable	48,281
Aggregate Intrinsic Value, Vested and expected to vest	$57,051

Stockbased_Compensation_Restri

Stock-based Compensation - Restricted Stock Unit Activities (Detail) (Unvested restricted stock units [Member], USD $)	6 Months Ended
	Jul. 31, 2014
Unvested restricted stock units [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares, Unvested, beginning balance	1,410,089
Shares, Granted	73,667
Shares, Vested	-202,644
Shares, Forfeited	-25,902
Shares, Unvested, ending balance	1,255,210
Weighted-Average Grant-Date Fair Value, Unvested, beginning balance	$14.02
Weighted-Average Grant-Date Fair Value, Granted	$29.93
Weighted-Average Grant-Date Fair Value, Vested	$13.89
Weighted-Average Grant-Date Fair Value, Forfeited	$13.46
Weighted-Average Grant-Date Fair Value, Unvested, ending balance	$14.99

Net_Income_Per_Ordinary_Share_1

Net Income Per Ordinary Share - Computation of Basic and Diluted Net Income Per Ordinary Share (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Numerator:	'	'	'	'
Net income	$9,310	$6,254	$14,570	$10,995
Less: amount allocable to unvested early exercised options	-2	-8	-4	-17
Net income allocable to ordinary shareholders - basic	9,308	6,246	14,566	10,978
Undistributed earnings reallocated to ordinary shareholders	'	1	'	1
Net income allocable to ordinary shareholders - diluted	$9,308	$6,247	$14,566	$10,979
Denominator:	'	'	'	'
Weighted-average ordinary shares outstanding	29,426,935	27,443,622	29,206,936	27,273,376
Less: weighted-average unvested early exercised options subject to repurchase	-5,735	-34,279	-8,425	-41,234
Weighted-average ordinary shares - basic	29,421,200	27,409,343	29,198,511	27,232,142
Weighted-average ordinary shares - basic	29,421,200	27,409,343	29,198,511	27,232,142
Effect of potentially dilutive securities:	'	'	'	'
Employee stock options	1,879,067	2,046,623	1,994,912	1,867,695
Restricted stock units	599,234	159,434	627,368	150,541
Employee stock purchase plan	'	231,278	10,698	201,048
Warrants to purchase ordinary shares	'	1,998	'	4,948
Weighted-average ordinary shares - diluted	31,899,501	29,848,676	31,831,489	29,456,374
Net income per ordinary share:	'	'	'	'
Basic	$0.32	$0.23	$0.50	$0.40
Diluted	$0.29	$0.21	$0.46	$0.37

Net_Income_Per_Ordinary_Share_2

Net Income Per Ordinary Share - Weighted-Average Potentially Dilutive Securities Excluded from Computation of Diluted Net Income Per Ordinary Share (Detail)	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	315,233	136,986	254,307	291,202
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	193,633	102,707	156,550	246,817
Restricted stock units [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	52,978	'	42,167	3,151
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	62,887	'	47,165	'
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	5,735	34,279	8,425	41,234

Income_Taxes_Summary_of_Report

Income Taxes - Summary of Reported Income Tax (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Income tax expense	$893	$667	$1,609	$1,140

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Income Tax Disclosure [Abstract]	'	'	'	'
Effective tax rate	8.80%	9.60%	9.90%	9.40%
Unrecognized tax benefits	$3.60	'	$3.60	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013	Jan. 31, 2014	Jul. 31, 2014	Jan. 31, 2014
						Indemnification agreement [Member]	Indemnification agreement [Member]
Loss Contingencies [Line Items]	'	'	'	'	'	'	'
Net operating lease expenses	$1,500,000	$1,300,000	$2,800,000	$2,400,000	'	'	'
Total manufacturing purchase commitments	18,400,000	'	18,400,000	'	13,700,000	'	'
Payments under indemnification obligations	'	'	'	'	'	0	0
Liabilities recorded under indemnification obligations	'	'	'	'	'	$0	$0

Commitments_and_Contingencies_2

Commitments and Contingencies - Future Annual Minimum Lease Payments (Detail) (USD $)	Jul. 31, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2015	$2,687
2016	5,079
2017	4,622
2018	1,381
2019	238
Total future annual minimum lease payments	$14,007

Segment_Reporting_Additional_I

Segment Reporting - Additional Information (Detail) (USD $)

6 Months Ended

6 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

In Thousands, unless otherwise specified

Jul. 31, 2014

Jan. 31, 2014

Jul. 31, 2014

Jan. 31, 2014

Jul. 31, 2014

Jan. 31, 2014

Jul. 31, 2014

Jul. 31, 2013

Jul. 31, 2014

Jul. 31, 2013

Jul. 31, 2014

Jul. 31, 2013

Jul. 31, 2014

Jul. 31, 2013

Segment

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Wintech and Chicony [Member]

Accounts receivable [Member]

Accounts receivable [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Sales revenue, net [Member]

Credit concentration risk [Member]

Credit concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Customer concentration risk [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Concentration Risk [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of reportable segment

1

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of revenue or accounts receivable

'

'

'

'

10.00%

10.00%

88.00%

87.00%

87.00%

84.00%

10.00%

10.00%

10.00%

10.00%

Accounts receivable

$26,833

$18,837

$23,600

$15,900

'

'

'

'

'

'

'

'

'

'

Segment_Reporting_Companys_Rev

Segment Reporting - Company's Revenue by Geographic Region (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	$46,968	$37,710	$87,889	$71,651
Hong Kong [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	41,999	33,195	77,393	61,969
Asia Pacific [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	585	446	1,218	702
United States [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	1,721	1,242	3,868	3,847
North America [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	1,445	1,071	2,716	2,033
Europe [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	$1,218	$1,756	$2,694	$3,100

RelatedParty_Transactions_Addi

Related-Party Transactions - Additional Information (Detail) (Related party [Member], USD $)	3 Months Ended		6 Months Ended
In Millions, unless otherwise specified	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2017
							Scenario, Forecast [Member]
Related Party Transaction [Line Items]	'	'	'	'	'	'	'
Percentage of entity's voting stock owned by related party	10.00%	'	10.00%	'	'	'	'
Total commitment payment of license	'	'	'	'	'	'	$6.90
Payment for license fees	0.6	0.4	1	0.9	'	'	'
Operating lease expenses related to license commitments included in research and development cost	0.5	0.4	0.7	0.9	'	'	'
Percentage of investor own voting stock	'	'	'	'	'	4.60%	'
Recognized revenue from related party	30.3	22.1	58.5	35.5	'	'	'
Account receivables from related party	$12.50	'	$12.50	'	$7.90	'	'