Ambarella (AMBA) 10-Q 12 Dec 13 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Oct. 31, 2013
Document And Entity Information [Abstract]	'
Document Type	'10-Q
Amendment Flag	'false
Document Period End Date	31-Oct-13
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q3
Trading Symbol	'AMBA
Entity Registrant Name	'AMBARELLA INC
Entity Central Index Key	'0001280263
Current Fiscal Year End Date	'--01-31
Entity Filer Category	'Non-accelerated Filer
Entity Common Stock, Shares Outstanding	28,212,643

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Oct. 31, 2013	Jan. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash	$128,051	$100,494
Accounts receivable, net	25,449	20,153
Inventories	13,010	8,918
Restricted cash	3	3
Deferred tax assets, current	1,073	1,220
Prepaid expenses and other current assets	1,998	2,360
Total current assets	169,584	133,148
Property and equipment, net	3,025	2,536
Deferred tax assets, non-current	1,105	938
Other assets	1,970	1,981
Total assets	175,684	138,603
Current liabilities:	'	'
Accounts payable	14,139	7,051
Accrued liabilities	12,066	14,042
Income taxes payable	77	286
Deferred revenue, current	3,552	3,451
Total current liabilities	29,834	24,830
Other long-term liabilities	1,427	1,441
Total liabilities	31,261	26,271
Commitments and contingencies (Note 10)	'	'
Shareholders' equity:	'	'
Preference shares, $0.00045 par value per share, 20,000,000 shares authorized and no shares issued and outstanding at October 31, 2013 and January 31, 2013, respectively	'	'
Ordinary shares, $0.00045 par value per share, 200,000,000 shares authorized at October 31, 2013 and January 31, 2013, respectively; 28,212,643 shares issued and outstanding at October 31, 2013; 27,035,074 shares issued and outstanding at January 31, 2013	13	12
Additional paid-in capital	103,880	91,911
Retained earnings	40,530	20,409
Total shareholders' equity	144,423	112,332
Total liabilities and shareholders' equity	$175,684	$138,603

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Oct. 31, 2013	Jan. 31, 2013
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	28,212,643	27,035,074
Ordinary shares, shares outstanding	28,212,643	27,035,074

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Income Statement [Abstract]	'	'	'	'
Revenue	$45,990	$35,669	$117,641	$89,548
Cost of revenue	16,689	12,679	43,356	28,821
Gross profit	29,301	22,990	74,285	60,727
Operating expenses	'	'	'	'
Research and development	13,476	10,802	35,767	31,631
Selling, general and administrative	5,761	4,603	16,303	12,812
Total operating expenses	19,237	15,405	52,070	44,443
Income from operations	10,064	7,585	22,215	16,284
Other income (loss), net	-12	137	-28	139
Income before income taxes	10,052	7,722	22,187	16,423
Provision for income taxes	926	1,005	2,066	1,878
Net income	$9,126	$6,717	$20,121	$14,545
Net income per share attributable to ordinary shareholders:	'	'	'	'
Basic	$0.33	$0.27	$0.73	$0.55
Diluted	$0.30	$0.25	$0.68	$0.51
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:	'	'	'	'
Basic	27,836,086	12,068,819	27,432,301	9,049,864
Diluted	30,355,230	13,415,091	29,754,837	10,506,293

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012
Cash flows from operating activities:	'	'
Net income	$20,121	$14,545
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Depreciation of property and equipment	789	545
Loss on disposal of long-lived assets	4	2
Amortization of other intangible assets	'	270
Stock-based compensation	5,660	3,441
Net excess income tax benefits associated with stock-based compensation	-513	'
Change in value of warrants	'	-149
Changes in operating assets and liabilities:	'	'
Accounts receivable	-5,296	-8,758
Inventories	-4,092	-2,355
Prepaid expenses and other current assets	362	-290
Deferred tax assets	-20	-472
Other assets	9	17
Accounts payable	7,088	2,435
Accrued liabilities	-1,588	4,026
Income taxes payable	304	585
Deferred revenue	101	-4,790
Net cash provided by operating activities	22,929	9,052
Cash flows from investing activities:	'	'
Restricted Cash	'	247
Net proceeds from disposal of fixed assets	13	'
Purchase of property and equipment	-1,384	-997
Net cash used in investing activities	-1,371	-750
Cash flows from financing activities:	'	'
Proceeds from exercise of stock options, warrants, and employee stock purchase plan withholding, net of repurchase of stock options	5,511	933
Payment for initial public offering cost	-25	-727
Proceeds from initial public offering, net of underwriting discounts and commissions	'	27,368
Net excess income tax benefits associated with stock-based compensation	513	'
Net cash provided by financing activities	5,999	27,574
Net increase in cash and cash equivalents	27,557	35,876
Cash and cash equivalents at beginning of period	100,494	58,944
Cash and cash equivalents at end of period	128,051	94,820
Supplemental disclosure of cash flow information:	'	'
Cash paid for income taxes	1,394	1,897
Supplemental disclosure of noncash investing activities:	'	'
Increase in accrued liabilities related to non-monetary assets purchases	33	147
Supplemental disclosure of noncash financing activities:	'	'
Increase in accrued liabilities related to non-monetary financing activities	'	1,245
Conversion of convertible preference shares to ordinary shares	'	50,900
Conversion of convertible preference share warrants to ordinary share warrants	'	$110

Organization_and_Summary_of_Si

Organization and Summary of Significant Accounting Policies	9 Months Ended
	Oct. 31, 2013
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 2013 fiscal year filed with the SEC on April 4, 2013 (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, and 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. Such estimates include (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; (v) warranty obligations; (vi) the valuation of stock-based compensation and equity 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. Actual results could differ from those estimates.
	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 the Company’s 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 11 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 and accounts receivable. The Company places its cash primarily in checking and money market accounts with reputable financial institutions. 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 Company does not hold or issue financial instruments for trading purposes.
	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 basis has been established and, accordingly, any associated reserve is not reversed until the inventory is sold or scrapped. The Company has not recognized any material inventory loss to date.
	Internal-Use Software
	The Company capitalizes certain software that is acquired and developed solely for internal use. The capitalization costs include fees for services provided to develop software during the application development stage, costs incurred to obtain software, travel expenses incurred and payroll related costs for employees who are directly associated with and who directly devote time to the project. The capitalization begins when the preliminary project stage is completed and ceases no later than the point at which the project is substantially complete and ready for its intended use after all substantial testing is completed. The internal-use software is amortized over its estimated useful life. Repairs and maintenance are charged to expense as incurred. As of October 31, 2013, the Company has capitalized approximately $1.1 million of internal-use software and has been recorded in property and equipment, net on the condensed consolidated balance sheet.
	Revenue Recognition
	The Company generates revenue from the sale 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 condensed consolidated balance sheets. Any price adjustments are recorded as a change to deferred revenue at the time the adjustments are agreed upon.
	Arrangements with certain OEM customers provide for pricing that is dependent upon the end products into which the Company’s SoCs are used. These arrangements may also entitle the Company to a share of the product margin ultimately realized by the OEM. The minimum guaranteed amount of revenue related to the sale of products subject to these arrangements is recognized when all other elements of revenue recognition are met. Any amounts at the date of shipment invoiced in excess of the minimum guaranteed contract price are deferred until the additional amounts the Company is entitled to are fixed or determinable. Additional amounts earned by the Company resulting from margin sharing arrangements and determination of the end products into which the products are ultimately incorporated are recognized when end customer sales volume is reported to the Company.
	The Company also 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 revenue from those licenses was not material for the nine months ended October 31, 2013 and 2012, respectively.
	Cost of Revenue
	Cost of revenue includes cost of materials, cost associated with packaging and assembly, testing and shipping, cost of personnel, stock-based compensation, logistics and quality assurance, warranty cost, royalty expense, write-downs of inventories and allocation of overhead.
	Income Taxes
	The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements or tax returns. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized.
	The Company applies authoritative guidance for the accounting for uncertainty in income taxes. The guidance requires that tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. Upon estimating the Company’s tax positions and tax benefits, the Company considered and evaluated numerous factors, which may require periodic adjustments and which may not reflect the final tax liabilities. The Company adjusts its financial statements to reflect only those tax positions that are more likely than not to be sustained under examination.
	As part of the process of preparing condensed consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differing treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets, which are included in the condensed consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the condensed consolidated statements of operations become deductible expenses under applicable income tax laws, or loss or credit carryforwards are utilized.
	In assessing whether deferred tax assets may be realized, management considers whether it is more likely than not that some portion or all of deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income.
	The Company makes estimates and judgments about its future taxable income based on assumptions that are consistent with its plans and estimates. Should the actual amounts differ from estimates, the amount of valuation allowance could be materially impacted. Any adjustment to the deferred tax asset valuation allowance would be recorded in the 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 on an if-converted basis 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 ESPP, upon the release of vested restricted stock units, upon the conversion of its redeemable convertible preference shares and upon the exercise of warrants.
	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 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 Company’s computation of basic earnings per ordinary share.
	Comprehensive Income
	There are no differences between comprehensive income as defined by ASC 220, Comprehensive Income, and net income as reported in the Company’s condensed consolidated statements of operations.
	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. Early adoption and retrospective application are permitted. The Company has not yet adopted this guidance but does not expect the adoption of this guidance to have a significant impact on its financial position, results of operations, statement of cash flows or disclosures.

Inventories

Inventories	9 Months Ended
	Oct. 31, 2013
Inventory Disclosure [Abstract]	'
Inventories	'
	2. Inventories
	Inventory at October 31, 2013 and January 31, 2013 consisted of the following:
		As of		As of
		October 31, 2013		January 31, 2013
		(in thousands)
	Work-in-progress	$	8,322	$	3,012
	Finished goods		4,688		5,906
	Total	$	13,010	$	8,918

Property_and_Equipment_Net

Property and Equipment, Net	9 Months Ended
	Oct. 31, 2013
Property Plant And Equipment [Abstract]	'
Property and Equipment, Net	'
	3. Property and Equipment, Net
	Depreciation expense was approximately $0.3 million and $0.2 million for the three months ended October 31, 2013 and 2012, respectively. Depreciation expense was approximately $0.8 million and $0.5 million for the nine months ended October 31, 2013 and 2012, respectively. Property and equipment at October 31, 2013 and January 31, 2013 consisted of the following:
		As of			As of
		October 31, 2013			January 31, 2013
		(in thousands)
	Computer equipment and software	$	4,247		$	2,810
	Machinery and equipment		2,112			2,050
	Furniture and fixtures		413			397
	Leasehold improvements		1,195			642
	Construction in progress		—			827
			7,967			6,726
	Less: accumulated depreciation and amortization		(4,942	)		(4,190	)
	Total property and equipment, net	$	3,025		$	2,536
	In March 2013, the Company entered into a lease agreement of approximately 35,000 square feet for its new headquarters located in Santa Clara, California with an initial five-year term. Pursuant to the lease agreement, the Company agreed to pay certain construction costs. As of October 31, 2013, the Company had capitalized approximately $0.7 million of leasehold improvement as a result of the construction, which will be depreciated over the term of the lease.
	In August 2012, the Company began implementation of its enterprise resources planning (“ERP”) system. As of October 31, 2013, the Company capitalized approximately $1.1 million of internal-use software related to the ERP implementation project and amortized over an estimated economic useful life of three years under a straight-line method.

Accrued_Liabilities

Accrued Liabilities	9 Months Ended
	Oct. 31, 2013
Payables And Accruals [Abstract]	'
Accrued Liabilities	'
	4. Accrued Liabilities
	Accrued liabilities at October 31, 2013 and January 31, 2013 consisted of the following:
		As of		As of
		October 31, 2013		January 31, 2013
		(in thousands)
	Accrued employee compensation	$	7,385	$	8,599
	Refundable exercised unvested options		91		210
	Accrued warranty		292		352
	Accrued rebates		257		272
	Accrued product development costs		3,019		2,875
	Other accrued liabilities		1,022		1,734
	Total accrued liabilities	$	12,066	$	14,042

Deferred_Revenue_and_Deferred_

Deferred Revenue and Deferred Cost	9 Months Ended
	Oct. 31, 2013
Revenue Recognition [Abstract]	'
Deferred Revenue and Deferred Cost	'
	5. Deferred Revenue and Deferred Cost
	Deferred revenue and related cost at October 31, 2013 and January 31, 2013 consisted of the following:
		As of			As of
		October 31, 2013			January 31, 2013
		(in thousands)
	Deferred revenue on product shipments	$	4,487		$	3,827
	Deferred revenue from licenses		400			485
	Deferred cost of revenue on product shipments		(1,335	)		(861	)
	Total deferred income	$	3,552		$	3,451

Capital_Stock

Capital Stock	9 Months Ended
	Oct. 31, 2013
Equity [Abstract]	'
Capital Stock	'
	6. 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 October 31, 2013 and January 31, 2013, respectively.
	Warrants
	In connection with a financing agreement in 2004, the Company issued warrants to purchase 36,292 redeemable convertible preference shares at an exercise price of $3.582 per share. Upon the completion of the IPO, the warrants to purchase redeemable convertible preference shares converted to warrants to purchase ordinary shares. As of October 31, 2013, the warrants were fully exercised and were no longer outstanding.
	Ordinary shares
	At October 31, 2013 and January 31, 2013, a total of 200,000,000 ordinary shares were authorized. As of October 31, 2013 and January 31, 2013, the following ordinary shares were reserved for future issuance:
		As of		As of
		October 31, 2013		January 31, 2013
	Shares reserved for options and restricted stock units		6,235,400		5,818,126
	Shares reserved for employee stock purchase plan		456,410		460,445
	Shares reserved for warrants		—		36,292

Stockbased_Compensation

Stock-based Compensation	9 Months Ended
	Oct. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Stock-based Compensation	'
	7. Stock-based Compensation
	The following table presents the classification of stock-based compensation for the periods indicated:
		Three Months Ended October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
		(in thousands)
	Stock-based compensation:
	Cost of revenue	$	47		$	30		$	115		$	59
	Research and development		1,385			905			3,259			1,979
	Selling, general and administrative		1,029			550			2,286			1,403
	Total stock-based compensation	$	2,461		$	1,485		$	5,660		$	3,441
	As of October 31, 2013, total unrecognized compensation cost related to unvested stock options and unvested restricted stock units was $5.9 million and $18.2 million, respectively, and is expected to be recognized over a weighted-average period of 1.96 years and 3.21 years, respectively. As of January 31, 2013, total unrecognized compensation cost related to unvested stock options and unvested restricted stock units was $7.3 million and $2.4 million, respectively, and is expected to be recognized over a weighted-average period of 2.26 years and 1.77 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 October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
	Stock Options:
	Volatility		65	%		66	%		65	%		66	%
	Risk-free interest rate		2.03	%		0.89	%		1.44	%		0.93	%
	Expected term (years)		6.05			6.05			6.05			6.05
	Dividend yield		0	%		0	%		0	%		0	%
	Employee stock purchase plan awards:
	Volatility		52	%		51	%		52	%		51	%
	Risk-free interest rate		0.04	%		0.18	%		0.04	%		0.18	%
	Expected term (years)		0.5			0.94			0.5			0.94
	Dividend yield		0	%		0	%		0	%		0	%
	The following table summarizes stock option activities for the nine months ended October 31, 2013:
		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, 2013		4,344,535			6.07
	Granted		192,220			15.9		$	9.5
	Exercised		(713,498	)		5.33					$	8,239
	Forfeited		(59,901	)		9.88
	Outstanding at October 31, 2013		3,763,356			6.65									6.44	$	52,314
	Exercisable at October 31, 2013		2,839,311			5.62									5.88	$	42,405
	Vested and expected to vest at October 31, 2013		3,715,813			6.6									6.41	$	51,819
	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 vested and expected-to-vest 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 $20.55 on October 31, 2013, 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.
	On August 27, 2013, upon recommendation by the Company’s compensation committee, the Company’s board of directors granted awards of restricted stock units (“RSU”) covering a total of 1,058,860 ordinary shares that vest based on service conditions and a total of 154,500 ordinary shares that vest based on a combination of service and performance conditions. The fair value on the grant date was $14.56 per ordinary share. Pursuant to the terms of the service condition awards, 1/16th of the RSUs shall vest every 3 months following the vesting commencement date, so as to be 100% vested on the fourth anniversary of the vesting commencement date. Pursuant to the terms of the performance condition awards, 1/8th of the RSUs shall vest every 3 months following the vesting commencement date, so as to be 100% vested on the second anniversary of the vesting commencement date; provided, however, that notwithstanding the foregoing, the RSUs shall not vest at all until the performance conditions are achieved and are subject to the RSU holder continuing to provide services to the Company through such vesting dates. The vesting commencement date for the performance condition RSUs will begin upon achievement of financial targets for the fiscal year 2014. The performance condition RSUs shall automatically be forfeited in their entirety, without any cost to or action by the Company, if there has been no achievement of the fiscal year 2014 financial targets.
	The following table summarizes restricted stock unit activities for the nine months ended October 31, 2013:
		Shares			Weighted-
					Average
					Grant-Date
					Fair Value
	Unvested at January 31, 2013		339,217		$	9.99
	Granted		1,240,472			14.58
	Released		(85,806	)		10.19
	Forfeited		(10,052	)		10.63
	Unvested at October 31, 2013		1,483,831		$	13.81
	As of October 31, 2013, the aggregate intrinsic value of unvested restricted stock units was $30.5 million.
	Non-employee Stock-based Compensation
	The fair value of awards granted to non-employees is determined on the date of grant and remeasured at the end of each reporting period until such awards vest. The non-employee stock-based compensation was not material for the nine months ended October 31, 2013 and 2012, respectively.

Net_Income_Per_Ordinary_Share

Net Income Per Ordinary Share	9 Months Ended
	Oct. 31, 2013
Earnings Per Share [Abstract]	'
Net Income Per Ordinary Share	'
	8. 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 October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
		(in thousands, except share and per share data)
	Numerator:
	Net income	$	9,126		$	6,717		$	20,121		$	14,545
	Less: amount allocable to preference shareholders		—			(3,456	)		—			(9,517	)
	Less: amount allocable to unvested early exercised options		(8	)		(18	)		(27	)		(53	)
	Net income allocable to ordinary shareholders - basic	$	9,118		$	3,243		$	20,094		$	4,975
	Undistributed earnings reallocated to ordinary shareholders		—			155			2			432
	Net income allocable to ordinary shareholders - diluted	$	9,118		$	3,398		$	20,096		$	5,407
	Denominator:
	Weighted-average ordinary shares outstanding		27,861,176			12,137,555			27,469,309			9,146,617
	Less: weighted-average unvested early exercised options subject to repurchase		(25,090	)		(68,736	)		(37,008	)		(96,753	)
	Weighted-average ordinary shares - basic		27,836,086			12,068,819			27,432,301			9,049,864
	Effect of potentially dilutive securities:
	Employee stock options		2,082,777			1,346,272			1,939,389			1,456,429
	Restricted stock units		313,832			—			204,971			—
	Employee stock purchase plan		122,535			—			174,877			—
	Warrants to purchase ordinary shares		—			—			3,299			—
	Weighted-average ordinary shares - diluted		30,355,230			13,415,091			29,754,837			10,506,293
	Net income per ordinary share:
	Basic	$	0.33		$	0.27		$	0.73		$	0.55
	Diluted	$	0.3		$	0.25		$	0.68		$	0.51
	Earnings per share (“EPS”) of ordinary shares was calculated using the two-class method required for participating securities. Prior to the date of the IPO, all series of redeemable convertible preference shares were considered to be participating securities due to their non-cumulative dividend rights. In connection with the Company’s IPO in October 2012, all outstanding redeemable convertible preference shares converted to ordinary shares. 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 were excluded from the computation of diluted net income per ordinary share as their effect would have been antidilutive:
		Three Months Ended October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
	Options to purchase ordinary shares		155,940			2,245,018			216,525			2,122,643
	Restricted stock units		—			242,014			2,101			80,671
	Employee stock purchase plan		42,387			81,422			14,128			28,321
	Allotment shares		—			216,000			—			72,000
	Early exercised options subject to repurchase		25,090			68,736			37,008			96,753
	Redeemable convertible preference shares (if-converted basis)		—			9,986,795			—			12,197,983
	Warrants to purchase redeemable convertible preference shares (if-converted basis)		—			27,219			—			33,246
			223,417			12,867,204			269,762			14,631,617

Income_Taxes

Income Taxes	9 Months Ended
	Oct. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	9. Income Taxes
	The Company reported the following income tax for the periods indicated:
		Three Months Ended October 31,				Nine Months Ended October 31,
		2013		2012		2013		2012
		(in thousands)
	Income tax expense	$	926	$	1,005	$	2,066	$	1,878
	The Company recognized income tax expense of approximately $1.0 million for the three months ended October 31, 2013 and 2012, respectively. The estimated effective tax rate was 9.2% and 13.0% for the three months ended October 31, 2013 and 2012, respectively. The Company recognized income tax expense of approximately $2.1 million and $1.9 million for the nine months ended October 31, 2013 and 2012, respectively. The estimated effective tax rate was 9.3% and 11.4% for the nine months ended October 31, 2013 and 2012, respectively. The effective tax rate for the nine months ended October 31, 2013 was lower than the effective tax rate for the nine months ended October 31, 2012 primarily due to a change in the mix of earnings in various geographic jurisdictions between the two periods.
	The Company files federal and state income tax returns in the United States and in various foreign jurisdictions. The tax years 2005 to 2013 remain open to examination by U.S. federal tax authorities and the tax years 2004 to 2010 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 our 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 October 31, 2013, the gross amount of unrecognized tax benefits was approximately $3.2 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	9 Months Ended
	Oct. 31, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	10. Commitments and Contingencies
	The Company leases its principal facilities and time-based software licenses under operating agreements with various expiration dates through April 2018. In March 2013, the Company entered into a lease agreement for approximately 35,000 square feet for its new Santa Clara, California headquarters. The lease has an initial five-year term and terminates in April 2018. The monthly basic rent obligation for this facility initially will be approximately $44,550, increasing annually to approximately $65,400 in 2017. The average monthly basic rent expense over the term of the lease will be approximately $59,800. Net operating lease expenses for the three months ended October 31, 2013 and 2012 were approximately $1.2 million and $1.1 million, respectively. Net operating lease expenses for the nine months ended October 31, 2013 and 2012 were approximately $3.6 million and $3.2 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
		October 31, 2013
	Fiscal Year	(in thousands)
	2014	$	1,144
	2015		1,702
	2016		1,670
	2017		1,492
	2018		1,386
		$	7,394
	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 October 31, 2013 and January 31, 2013, total manufacturing purchase commitments were approximately $12.4 million and $15.1 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 October 31, 2013 and January 31, 2013.

Segment_Reporting

Segment Reporting	9 Months Ended
	Oct. 31, 2013
Segment Reporting [Abstract]	'
Segment Reporting	'
	11. Segment Reporting
	The Company operates in one reportable segment related to the development and sales of low-power, high-definition video products. The Chief Executive Officer of the Company has been identified as the Chief Operating Decision Maker (the “CODM”) and manages the Company’s operations as a whole and for the purpose of evaluating financial performance and allocating resources, the CODM reviews financial information presented on a consolidated basis accompanied by information by customer and geographic region.
	Geographic Revenue
	The following table sets forth the Company’s revenue by geographic region for the periods indicated:
		Three Months Ended				Nine Months Ended
		October 31,				October 31,
		2013		2012		2013		2012
		(in thousands)
	Hong Kong	$	39,502	$	31,036	$	101,471	$	77,126
	Asia Pacific		942		63		1,644		314
	United States		1,710		1,931		5,557		6,335
	North America		1,369		783		3,402		1,431
	Europe		2,467		1,856		5,567		4,342
	Total revenue	$	45,990	$	35,669	$	117,641	$	89,548
	As of October 31, 2013, substantially all of the Company’s long-lived tangible assets are located in the Asia Pacific region.
	Major Customers
	The customers representing 10% or more of revenue and accounts receivable were Wintech, the Company’s logistic provider, and Chicony, a direct ODM customer, which combined accounted for approximately 86% and 78% of total revenue for the three months ended October 31, 2013 and 2012, respectively, and approximately 85% and 79% of total revenue for the nine months ended October 31, 2013 and 2012, respectively. Accounts receivable with these two customers combined accounted for approximately $22.9 million and $17.6 million as of October 31, 2013 and January 31, 2013, respectively.

RelatedParty_Transactions

Related-Party Transactions	9 Months Ended
	Oct. 31, 2013
Related Party Transactions [Abstract]	'
Related-Party Transactions	'
	12. 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 board of directors or if it is a significant shareholder and has material business transactions with the Company.
	Starting from the fiscal year 2008, the Company entered into several software license agreements 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 agreements, the Company committed to pay an aggregate amount of $10.2 million payable through January 2014. The Company paid $0.4 million in license fees in each of the three months ended October 31, 2013 and 2012. The Company paid $1.3 million in license fees in each of the nine months ended October 31, 2013 and 2012. Operating lease expenses related to these agreements included in research and development cost were approximately $0.4 million in each of the three months ended October 31, 2013 and 2012. Operating lease expenses related to these agreements included in research and development cost were approximately $1.3 million in each of the nine months ended October 31, 2013 and 2012.
	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. The Company recognized revenue from sales to Wintech of approximately $27.7 million and $21.4 million for the three months ended October 31, 2013 and 2012, respectively. The Company recognized revenue from sales to Wintech of approximately $63.3 million and $60.8 million for the nine months ended October 31, 2013 and 2012, respectively. As of October 31, 2013 and January 31, 2013, the Company had receivables from Wintech of approximately $11.5 million and $8.2 million, respectively.

Organization_and_Summary_of_Si1

Organization and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Oct. 31, 2013
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 2013 fiscal year filed with the SEC on April 4, 2013 (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, and 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. Such estimates include (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; (v) warranty obligations; (vi) the valuation of stock-based compensation and equity 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. Actual results could differ from those estimates.
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 the Company’s 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 11 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 and accounts receivable. The Company places its cash primarily in checking and money market accounts with reputable financial institutions. 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 Company does not hold or issue financial instruments for trading purposes.
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 basis has been established and, accordingly, any associated reserve is not reversed until the inventory is sold or scrapped. The Company has not recognized any material inventory loss to date.
Internal-Use Software	'
	Internal-Use Software
	The Company capitalizes certain software that is acquired and developed solely for internal use. The capitalization costs include fees for services provided to develop software during the application development stage, costs incurred to obtain software, travel expenses incurred and payroll related costs for employees who are directly associated with and who directly devote time to the project. The capitalization begins when the preliminary project stage is completed and ceases no later than the point at which the project is substantially complete and ready for its intended use after all substantial testing is completed. The internal-use software is amortized over its estimated useful life. Repairs and maintenance are charged to expense as incurred. As of October 31, 2013, the Company has capitalized approximately $1.1 million of internal-use software and has been recorded in property and equipment, net on the condensed consolidated balance sheet.
Revenue Recognition	'
	Revenue Recognition
	The Company generates revenue from the sale 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 condensed consolidated balance sheets. Any price adjustments are recorded as a change to deferred revenue at the time the adjustments are agreed upon.
	Arrangements with certain OEM customers provide for pricing that is dependent upon the end products into which the Company’s SoCs are used. These arrangements may also entitle the Company to a share of the product margin ultimately realized by the OEM. The minimum guaranteed amount of revenue related to the sale of products subject to these arrangements is recognized when all other elements of revenue recognition are met. Any amounts at the date of shipment invoiced in excess of the minimum guaranteed contract price are deferred until the additional amounts the Company is entitled to are fixed or determinable. Additional amounts earned by the Company resulting from margin sharing arrangements and determination of the end products into which the products are ultimately incorporated are recognized when end customer sales volume is reported to the Company.
	The Company also 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 revenue from those licenses was not material for the nine months ended October 31, 2013 and 2012, respectively.
Cost of Revenue	'
	Cost of Revenue
	Cost of revenue includes cost of materials, cost associated with packaging and assembly, testing and shipping, cost of personnel, stock-based compensation, logistics and quality assurance, warranty cost, royalty expense, write-downs of inventories and allocation of overhead.
Income Taxes	'
	Income Taxes
	The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements or tax returns. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized.
	The Company applies authoritative guidance for the accounting for uncertainty in income taxes. The guidance requires that tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. Upon estimating the Company’s tax positions and tax benefits, the Company considered and evaluated numerous factors, which may require periodic adjustments and which may not reflect the final tax liabilities. The Company adjusts its financial statements to reflect only those tax positions that are more likely than not to be sustained under examination.
	As part of the process of preparing condensed consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differing treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets, which are included in the condensed consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the condensed consolidated statements of operations become deductible expenses under applicable income tax laws, or loss or credit carryforwards are utilized.
	In assessing whether deferred tax assets may be realized, management considers whether it is more likely than not that some portion or all of deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income.
	The Company makes estimates and judgments about its future taxable income based on assumptions that are consistent with its plans and estimates. Should the actual amounts differ from estimates, the amount of valuation allowance could be materially impacted. Any adjustment to the deferred tax asset valuation allowance would be recorded in the 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 on an if-converted basis 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 ESPP, upon the release of vested restricted stock units, upon the conversion of its redeemable convertible preference shares and upon the exercise of warrants.
	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 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 Company’s computation of basic earnings per ordinary share.
Comprehensive Income	'
	Comprehensive Income
	There are no differences between comprehensive income as defined by ASC 220, Comprehensive Income, and net income as reported in the Company’s condensed consolidated statements of operations.
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. Early adoption and retrospective application are permitted. The Company has not yet adopted this guidance but does not expect the adoption of this guidance to have a significant impact on its financial position, results of operations, statement of cash flows or disclosures.

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Oct. 31, 2013
Inventory Disclosure [Abstract]	'
Schedule of Inventory	'
	Inventory at October 31, 2013 and January 31, 2013 consisted of the following:
		As of		As of
		October 31, 2013		January 31, 2013
		(in thousands)
	Work-in-progress	$	8,322	$	3,012
	Finished goods		4,688		5,906
	Total	$	13,010	$	8,918

Property_and_Equipment_Net_Tab

Property and Equipment, Net (Tables)	9 Months Ended
	Oct. 31, 2013
Property Plant And Equipment [Abstract]	'
Schedule of Property and Equipment	'
	Property and equipment at October 31, 2013 and January 31, 2013 consisted of the following:
		As of			As of
		October 31, 2013			January 31, 2013
		(in thousands)
	Computer equipment and software	$	4,247		$	2,810
	Machinery and equipment		2,112			2,050
	Furniture and fixtures		413			397
	Leasehold improvements		1,195			642
	Construction in progress		—			827
			7,967			6,726
	Less: accumulated depreciation and amortization		(4,942	)		(4,190	)
	Total property and equipment, net	$	3,025		$	2,536

Accrued_Liabilities_Tables

Accrued Liabilities (Tables)	9 Months Ended
	Oct. 31, 2013
Payables And Accruals [Abstract]	'
Schedule of Accrued Liabilities	'
	Accrued liabilities at October 31, 2013 and January 31, 2013 consisted of the following:
		As of		As of
		October 31, 2013		January 31, 2013
		(in thousands)
	Accrued employee compensation	$	7,385	$	8,599
	Refundable exercised unvested options		91		210
	Accrued warranty		292		352
	Accrued rebates		257		272
	Accrued product development costs		3,019		2,875
	Other accrued liabilities		1,022		1,734
	Total accrued liabilities	$	12,066	$	14,042

Deferred_Revenue_and_Deferred_1

Deferred Revenue and Deferred Cost (Tables)	9 Months Ended
	Oct. 31, 2013
Revenue Recognition [Abstract]	'
Schedule of Deferred Revenue and Related Cost	'
	Deferred revenue and related cost at October 31, 2013 and January 31, 2013 consisted of the following:
		As of			As of
		October 31, 2013			January 31, 2013
		(in thousands)
	Deferred revenue on product shipments	$	4,487		$	3,827
	Deferred revenue from licenses		400			485
	Deferred cost of revenue on product shipments		(1,335	)		(861	)
	Total deferred income	$	3,552		$	3,451

Capital_Stock_Tables

Capital Stock (Tables)	9 Months Ended
	Oct. 31, 2013
Equity [Abstract]	'
Schedule of Ordinary Shares Reserved for Future Issuance	'
	As of October 31, 2013 and January 31, 2013, the following ordinary shares were reserved for future issuance:
		As of		As of
		October 31, 2013		January 31, 2013
	Shares reserved for options and restricted stock units		6,235,400		5,818,126
	Shares reserved for employee stock purchase plan		456,410		460,445
	Shares reserved for warrants		—		36,292

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	9 Months Ended
	Oct. 31, 2013
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 October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
		(in thousands)
	Stock-based compensation:
	Cost of revenue	$	47		$	30		$	115		$	59
	Research and development		1,385			905			3,259			1,979
	Selling, general and administrative		1,029			550			2,286			1,403
	Total stock-based compensation	$	2,461		$	1,485		$	5,660		$	3,441
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 October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
	Stock Options:
	Volatility		65	%		66	%		65	%		66	%
	Risk-free interest rate		2.03	%		0.89	%		1.44	%		0.93	%
	Expected term (years)		6.05			6.05			6.05			6.05
	Dividend yield		0	%		0	%		0	%		0	%
	Employee stock purchase plan awards:
	Volatility		52	%		51	%		52	%		51	%
	Risk-free interest rate		0.04	%		0.18	%		0.04	%		0.18	%
	Expected term (years)		0.5			0.94			0.5			0.94
	Dividend yield		0	%		0	%		0	%		0	%
Stock Option Activities	'
	The following table summarizes stock option activities for the nine months ended October 31, 2013:
		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, 2013		4,344,535			6.07
	Granted		192,220			15.9		$	9.5
	Exercised		(713,498	)		5.33					$	8,239
	Forfeited		(59,901	)		9.88
	Outstanding at October 31, 2013		3,763,356			6.65									6.44	$	52,314
	Exercisable at October 31, 2013		2,839,311			5.62									5.88	$	42,405
	Vested and expected to vest at October 31, 2013		3,715,813			6.6									6.41	$	51,819
Restricted Stock Unit Activities	'
	The following table summarizes restricted stock unit activities for the nine months ended October 31, 2013:
		Shares			Weighted-
					Average
					Grant-Date
					Fair Value
	Unvested at January 31, 2013		339,217		$	9.99
	Granted		1,240,472			14.58
	Released		(85,806	)		10.19
	Forfeited		(10,052	)		10.63
	Unvested at October 31, 2013		1,483,831		$	13.81

Net_Income_Per_Ordinary_Share_

Net Income Per Ordinary Share (Tables)	9 Months Ended
	Oct. 31, 2013
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 October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
		(in thousands, except share and per share data)
	Numerator:
	Net income	$	9,126		$	6,717		$	20,121		$	14,545
	Less: amount allocable to preference shareholders		—			(3,456	)		—			(9,517	)
	Less: amount allocable to unvested early exercised options		(8	)		(18	)		(27	)		(53	)
	Net income allocable to ordinary shareholders - basic	$	9,118		$	3,243		$	20,094		$	4,975
	Undistributed earnings reallocated to ordinary shareholders		—			155			2			432
	Net income allocable to ordinary shareholders - diluted	$	9,118		$	3,398		$	20,096		$	5,407
	Denominator:
	Weighted-average ordinary shares outstanding		27,861,176			12,137,555			27,469,309			9,146,617
	Less: weighted-average unvested early exercised options subject to repurchase		(25,090	)		(68,736	)		(37,008	)		(96,753	)
	Weighted-average ordinary shares - basic		27,836,086			12,068,819			27,432,301			9,049,864
	Effect of potentially dilutive securities:
	Employee stock options		2,082,777			1,346,272			1,939,389			1,456,429
	Restricted stock units		313,832			—			204,971			—
	Employee stock purchase plan		122,535			—			174,877			—
	Warrants to purchase ordinary shares		—			—			3,299			—
	Weighted-average ordinary shares - diluted		30,355,230			13,415,091			29,754,837			10,506,293
	Net income per ordinary share:
	Basic	$	0.33		$	0.27		$	0.73		$	0.55
	Diluted	$	0.3		$	0.25		$	0.68		$	0.51
Weighted-Average Potentially Dilutive Securities Excluded from Computation of Diluted Net Income Per Ordinary Share	'
	The following weighted-average potentially dilutive securities were excluded from the computation of diluted net income per ordinary share as their effect would have been antidilutive:
		Three Months Ended October 31,						Nine Months Ended October 31,
		2013			2012			2013			2012
	Options to purchase ordinary shares		155,940			2,245,018			216,525			2,122,643
	Restricted stock units		—			242,014			2,101			80,671
	Employee stock purchase plan		42,387			81,422			14,128			28,321
	Allotment shares		—			216,000			—			72,000
	Early exercised options subject to repurchase		25,090			68,736			37,008			96,753
	Redeemable convertible preference shares (if-converted basis)		—			9,986,795			—			12,197,983
	Warrants to purchase redeemable convertible preference shares (if-converted basis)		—			27,219			—			33,246
			223,417			12,867,204			269,762			14,631,617

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Oct. 31, 2013
Income Tax Disclosure [Abstract]	'
Summary of Reported Income Tax	'
	The Company reported the following income tax for the periods indicated:
		Three Months Ended October 31,				Nine Months Ended October 31,
		2013		2012		2013		2012
		(in thousands)
	Income tax expense	$	926	$	1,005	$	2,066	$	1,878

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Oct. 31, 2013
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
		October 31, 2013
	Fiscal Year	(in thousands)
	2014	$	1,144
	2015		1,702
	2016		1,670
	2017		1,492
	2018		1,386
		$	7,394

Segment_Reporting_Tables

Segment Reporting (Tables)	9 Months Ended
	Oct. 31, 2013
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				Nine Months Ended
		October 31,				October 31,
		2013		2012		2013		2012
		(in thousands)
	Hong Kong	$	39,502	$	31,036	$	101,471	$	77,126
	Asia Pacific		942		63		1,644		314
	United States		1,710		1,931		5,557		6,335
	North America		1,369		783		3,402		1,431
	Europe		2,467		1,856		5,567		4,342
	Total revenue	$	45,990	$	35,669	$	117,641	$	89,548

Organization_and_Summary_of_Si2

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	Oct. 31, 2013
In Millions, unless otherwise specified
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
Capitalizes internal-use software	$1.10

Inventories_Schedule_of_Invent

Inventories - Schedule of Inventory (Detail) (USD $)	Oct. 31, 2013	Jan. 31, 2013
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Work-in-progress	$8,322	$3,012
Finished goods	4,688	5,906
Total	$13,010	$8,918

Property_and_Equipment_Net_Add

Property and Equipment, Net - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2013	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
	sqft
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Depreciation	'	$300,000	$200,000	$789,000	$545,000
Lease agreement new headquarters	35,000	'	'	'	'
Initial lease term	'5 years	'	'	'	'
Capitalized internal-use software	'	1,100,000	'	1,100,000	'
Leasehold improvement [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Capitalized leasehold improvement	'	700,000	'	700,000	'
Internal-use software [Member]	'	'	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'	'	'
Capitalized internal-use software	'	$1,100,000	'	$1,100,000	'
Estimated economic useful life	'	'	'	'3 years	'

Property_and_Equipment_Net_Sch

Property and Equipment, Net - Schedule of Property and Equipment (Detail) (USD $)	Oct. 31, 2013	Jan. 31, 2013
In Thousands, unless otherwise specified
Property Plant And Equipment [Abstract]	'	'
Computer equipment and software	$4,247	$2,810
Machinery and equipment	2,112	2,050
Furniture and fixtures	413	397
Leasehold improvements	1,195	642
Construction in progress	'	827
Property and equipment, gross	7,967	6,726
Less: accumulated depreciation and amortization	-4,942	-4,190
Total property and equipment, net	$3,025	$2,536

Accrued_Liabilities_Schedule_o

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) (USD $)	Oct. 31, 2013	Jan. 31, 2013
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]	'	'
Accrued employee compensation	$7,385	$8,599
Refundable exercised unvested options	91	210
Accrued warranty	292	352
Accrued rebates	257	272
Accrued product development costs	3,019	2,875
Other accrued liabilities	1,022	1,734
Total accrued liabilities	$12,066	$14,042

Deferred_Revenue_and_Deferred_2

Deferred Revenue and Deferred Cost - Schedule of Deferred Revenue and Related Cost (Detail) (USD $)	Oct. 31, 2013	Jan. 31, 2013
In Thousands, unless otherwise specified
Deferred Revenue Arrangement [Line Items]	'	'
Deferred cost of revenue on product shipments	($1,335)	($861)
Deferred revenue	3,552	3,451
Product shipments [Member]	'	'
Deferred Revenue Arrangement [Line Items]	'	'
Deferred revenue	4,487	3,827
Licenses [Member]	'	'
Deferred Revenue Arrangement [Line Items]	'	'
Deferred revenue	$400	$485

Capital_Stock_Additional_Infor

Capital Stock - Additional Information (Detail) (USD $)	Oct. 31, 2013	Jan. 31, 2013
Equity [Abstract]	'	'
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
Company issued warrants to purchase redeemable convertible preference shares, exercise price	'	3.582
Company issued warrants to purchase redeemable convertible preference shares	'	36,292
Total ordinary share warrants outstanding	0	36,292
Total ordinary shares authorized	200,000,000	200,000,000

Capital_Stock_Schedule_of_Ordi

Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance (Detail)	Oct. 31, 2013	Jan. 31, 2013
Options and restricted stock units [Member]	'	'
Class of Stock [Line Items]	'	'
Shares reserved	6,235,400	5,818,126
Employee stock purchase plan [Member]	'	'
Class of Stock [Line Items]	'	'
Shares reserved	456,410	460,445
Warrants [Member]	'	'
Class of Stock [Line Items]	'	'
Shares reserved	'	36,292

Stockbased_Compensation_Classi

Stock-based Compensation - Classification of Stock-based Compensation (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Stock-based compensation:	'	'	'	'
Total stock-based compensation	$2,461	$1,485	$5,660	$3,441
Cost of revenue [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	47	30	115	59
Research and development [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	1,385	905	3,259	1,979
Selling, general and administrative [Member]	'	'	'	'
Stock-based compensation:	'	'	'	'
Total stock-based compensation	$1,029	$550	$2,286	$1,403

Stockbased_Compensation_Additi

Stock-based Compensation - Additional Information (Detail) (USD $)	Oct. 31, 2013	Aug. 27, 2013	Oct. 31, 2013	Jan. 31, 2013	Oct. 31, 2013	Jan. 31, 2013	Aug. 27, 2013	Aug. 27, 2013
In Millions, except Share data, unless otherwise specified			Restricted stock units [Member]	Restricted stock units [Member]	Employee stock option [Member]	Employee stock option [Member]	Service condition restricted stock units [Member]	Service and performance conditioned restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'
Total unrecognized compensation cost, stock options	'	'	'	'	$5.90	$7.30	'	'
Total unrecognized compensation cost, restricted stock units	'	'	18.2	2.4	'	'	'	'
Weighted-average period	'	'	'3 years 2 months 16 days	'1 year 9 months 7 days	'1 year 11 months 16 days	'2 years 3 months 4 days	'	'
Closing price of ordinary shares	$20.55	'	'	'	'	'	'	'
Ordinary shares granted as awards of restricted stock units	'	'	1,240,472	'	'	'	1,058,860	154,500
Fair value on grant date per ordinary share	'	$14.56	'	'	'	'	'	'
Vesting period of RSUs	'	'	'	'	'	'	'1/16th of the RSUs shall vest each 3 months following the vesting commencement date, so as to be 100% vested on the fourth anniversary of the vesting commencement date	'1/8th of the RSUs shall vest each 3 months following the vesting commencement date, so as to be 100% vested on the second anniversary of the vesting commencement date
Aggregate intrinsic value of unvested restricted stock units	'	'	$30.50	'	'	'	'	'

Stockbased_Compensation_Weight

Stock-based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value (Detail)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Options to purchase ordinary shares [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Volatility	65.00%	66.00%	65.00%	66.00%
Risk-free interest rate	2.03%	0.89%	1.44%	0.93%
Expected term (years)	'6 years 18 days	'6 years 18 days	'6 years 18 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	52.00%	51.00%	52.00%	51.00%
Risk-free interest rate	0.04%	0.18%	0.04%	0.18%
Expected term (years)	'6 months	'11 months 9 days	'6 months	'11 months 9 days
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stockbased_Compensation_Stock_

Stock-based Compensation - Stock Option Activities (Detail) (USD $)	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Oct. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Shares, Outstanding	4,344,535
Shares, Granted	192,220
Shares, Exercised	-713,498
Shares, Forfeited	-59,901
Shares, Outstanding	3,763,356
Shares, Exercisable	2,839,311
Shares, Vested and expected to vest	3,715,813
Weighted-Average Exercise Price, Outstanding	$6.07
Weighted-Average Exercise Price, Granted	$15.90
Weighted-Average Exercise Price, Exercised	$5.33
Weighted-Average Exercise Price, Forfeited	$9.88
Weighted-Average Exercise Price, Outstanding	$6.65
Weighted-Average Exercise Price, Exercisable	$5.62
Weighted-Average Exercise Price, Vested and expected to vest	$6.60
Weighted-Average Grant-date Fair Value, Granted	$9.50
Total Intrinsic Value of options Exercised, Exercised	$8,239
Weighted-Average Remaining Contractual Term, Outstanding	'6 years 5 months 9 days
Weighted-Average Remaining Contractual Term, Exercisable	'5 years 10 months 17 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	'6 years 4 months 28 days
Aggregate Intrinsic Value, Outstanding	52,314
Aggregate Intrinsic Value, Exercisable	42,405
Aggregate Intrinsic Value, Vested and expected to vest	$51,819

Stockbased_Compensation_Restri

Stock-based Compensation - Restricted Stock Unit Activities (Detail) (Restricted stock units [Member], USD $)	9 Months Ended
	Oct. 31, 2013
Restricted stock units [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Shares, Unvested, beginning balance	339,217
Shares, Granted	1,240,472
Shares, Released	-85,806
Shares, Forfeited	-10,052
Shares, Unvested, ending balance	1,483,831
Weighted-Average Grant-Date Fair Value, Unvested beginning balance	$9.99
Weighted-Average Grant-Date Fair Value, Granted	$14.58
Weighted-Average Grant-Date Fair Value, Released	$10.19
Weighted-Average Grant-Date Fair Value, Forfeited	$10.63
Weighted-Average Grant-Date Fair Value, Unvested ending balance	$13.81

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		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Numerator:	'	'	'	'
Net income	$9,126	$6,717	$20,121	$14,545
Less: amount allocable to preference shareholders	'	-3,456	'	-9,517
Less: amount allocable to unvested early exercised options	-8	-18	-27	-53
Net income allocable to ordinary shareholders - basic	9,118	3,243	20,094	4,975
Undistributed earnings reallocated to ordinary shareholders	'	155	2	432
Net income allocable to ordinary shareholders - diluted	$9,118	$3,398	$20,096	$5,407
Denominator:	'	'	'	'
Weighted-average ordinary shares outstanding	27,861,176	12,137,555	27,469,309	9,146,617
Less: weighted-average unvested early exercised options subject to repurchase	-25,090	-68,736	-37,008	-96,753
Weighted-average ordinary shares - basic	27,836,086	12,068,819	27,432,301	9,049,864
Effect of potentially dilutive securities:	'	'	'	'
Employee stock options	2,082,777	1,346,272	1,939,389	1,456,429
Restricted stock units	313,832	'	204,971	'
Employee stock purchase plan	122,535	'	174,877	'
Warrants to purchase ordinary shares	'	'	3,299	'
Weighted-average ordinary shares - diluted	30,355,230	13,415,091	29,754,837	10,506,293
Net income per ordinary share:	'	'	'	'
Basic	$0.33	$0.27	$0.73	$0.55
Diluted	$0.30	$0.25	$0.68	$0.51

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		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	223,417	12,867,204	269,762	14,631,617
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	155,940	2,245,018	216,525	2,122,643
Restricted stock units [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	'	242,014	2,101	80,671
Employee stock purchase plan awards [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	42,387	81,422	14,128	28,321
Allotment shares [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	'	216,000	'	72,000
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	25,090	68,736	37,008	96,753
Redeemable convertible preference shares (if-converted basis) [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	'	9,986,795	'	12,197,983
Warrants to purchase redeemable convertible preference shares (if-converted basis) [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Antidilutive shares excluded from computation of earnings per share	'	27,219	'	33,246

Income_Taxes_Summary_of_Report

Income Taxes - Summary of Reported Income Tax (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Income Tax Disclosure [Abstract]	'	'	'	'
Income tax expense	$926	$1,005	$2,066	$1,878

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Income Tax Disclosure [Abstract]	'	'	'	'
Income tax expense	$926,000	$1,005,000	$2,066,000	$1,878,000
Estimated effective tax rate	9.20%	13.00%	9.30%	11.40%
Unrecognized tax benefits	$3,200,000	'	$3,200,000	'

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2013	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012	Jan. 31, 2013	31-May-13	Oct. 31, 2013	Jan. 31, 2013
	sqft						2017 [Member]	Indemnification Agreement [Member]	Indemnification Agreement [Member]
Loss Contingencies [Line Items]	'	'	'	'	'	'	'	'	'
Net operating lease expenses	'	$1,200,000	$1,100,000	$3,600,000	$3,200,000	'	'	'	'
Lease agreement rental area in square feet	35,000	'	'	'	'	'	'	'	'
Initial lease term	'5 years	'	'	'	'	'	'	'	'
Lease termination year	'2018-04	'	'	'	'	'	'	'	'
Monthly basic rent obligation	'	44,550	'	'	'	'	65,400	'	'
Average monthly basic rent expense	'	59,800	'	'	'	'	'	'	'
Total manufacturing purchase commitments	'	12,400,000	'	12,400,000	'	15,100,000	'	'	'
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 $)	Oct. 31, 2013
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014	$1,144
2015	1,702
2016	1,670
2017	1,492
2018	1,386
Total future annual minimum lease payments	$7,394

Segment_Reporting_Companys_Rev

Segment Reporting - Company's Revenue by Geographic Region (Detail) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	$45,990	$35,669	$117,641	$89,548
Hong Kong [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	39,502	31,036	101,471	77,126
Asia Pacific [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	942	63	1,644	314
United States [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	1,710	1,931	5,557	6,335
North America [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	1,369	783	3,402	1,431
Europe [Member]	'	'	'	'
Revenue from External Customer [Line Items]	'	'	'	'
Total revenue	$2,467	$1,856	$5,567	$4,342

Segment_Reporting_Additional_I

Segment Reporting - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012	Jan. 31, 2013
Concentration Risk [Line Items]	'	'	'	'	'
Accounts receivable	25,449	'	25,449	'	20,153
Wintech And Chicony [Member]	'	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'	'
Accounts receivable	22,900	'	22,900	'	17,600
Wintech And Chicony [Member] | Accounts Receivable [Member] | Credit Concentration Risk [Member] | Minimum [Member]	'	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'	'
Percentage of revenue or accounts receivable	10.00%	10.00%	10.00%	10.00%	10.00%
Wintech And Chicony [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]	'	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'	'
Percentage of revenue or accounts receivable	86.00%	78.00%	85.00%	79.00%	'
Wintech And Chicony [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Minimum [Member]	'	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'	'
Percentage of revenue or accounts receivable	10.00%	10.00%	10.00%	10.00%	10.00%

RelatedParty_Transactions_Addi

Related-Party Transactions - Additional Information (Detail) (Related Party [Member], USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012	Jan. 31, 2013
Related Party [Member]	'	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'	'
Percentage of entity's voting stock owned by related party	10.00%	10.00%	10.00%	10.00%	10.00%
Total commitment payment of license	$10.20	$10.20	$10.20	$10.20	$10.20
Payment for license fees	0.4	0.4	1.3	1.3	'
Operating lease expense related to license agreements included in research and development cost	0.4	0.4	1.3	1.3	'
Percentage of investor own voting stock	'	'	'	'	4.60%
Recognized revenue from related party	27.7	21.4	63.3	60.8	'
Account receivables from related party	$11.50	'	$11.50	'	$8.20