Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2013
Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Trading Symbol	AMBA
Entity Registrant Name	Ambarella Inc
Entity Central Index Key	0001280263
Current Fiscal Year End Date	--01-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding	27,035,074
Entity Public Float	$ 151

CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Current assets:
Cash	$ 100,494	$ 58,944
Accounts receivable, net	20,153	9,485
Inventories	8,918	6,786
Restricted cash	3	517
Deferred tax assets, current	1,220	861
Prepaid expenses and other current assets	2,360	1,226
Total current assets	133,148	77,819
Property and equipment, net	2,536	1,686
Deferred tax assets, non-current	938	426
Intangible assets, net	0	270
Other assets	1,981	1,538
Total assets	138,603	81,739
Current liabilities:
Accounts payable	6,674	6,481
Accrued liabilities	14,419	7,931
Income taxes payable	286	530
Deferred revenue, current	3,451	8,002
Total current liabilities	24,830	22,944
Deferred revenue, non-current	0	200
Other long-term liabilities	1,441	1,246
Total liabilities	26,271	24,390
Commitments and contingencies (Note 12)
Redeemable convertible preference shares (Note 8):
Series A, B, C and D redeemable convertible preference shares, $0.00045 par value per share- 5,611,111, 3,665,550, 3,027,777 and 2,222,222 shares authorized at January 31, 2012, respectively; 5,611,107, 3,629,253, 3,027,771 and 1,047,596 shares issued and outstanding at January 31, 2012, respectively; initial liquidation preference of $10,100, $13,000, $16,350 and $11,785 at January 31, 2012, respectively	0	50,900
Shareholders' equity:
Preference shares, $0.00045 par value per share, 20,000,000 shares authorized and no shares issued and outstanding at January 31, 2013; no shares authorized, issued and outstanding at January 31, 2012;	0	0
Ordinary shares, $0.00045 par value per share, 200,000,000 and 44,444,444 shares authorized at January 31, 2013 and at January 31, 2012, respectively; 27,035,074 shares issued and outstanding at January 31, 2013; 7,600,869 shares issued and outstanding at January 31, 2012	12	3
Additional paid-in capital	91,911	4,225
Retained earnings	20,409	2,221
Total shareholders' equity	112,332	6,449
Total liabilities, redeemable convertible preference shares and shareholders' equity	$ 138,603	$ 81,739

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Preference shares, par value	$ 0.00045	$ 0.00000
Preference shares, shares authorized	20,000,000	0
Preference shares, shares issued	0	0
Preference shares, shares outstanding	0	0
Ordinary shares, par value	$ 0.00045	$ 0.00045
Ordinary shares, shares authorized	200,000,000	44,444,444
Ordinary shares, shares issued	27,035,074	7,600,869
Ordinary shares, shares outstanding	27,035,074	7,600,869
Series A Redeemable convertible preference shares [Member]
Redeemable convertible preference shares, par value		$ 0.00045
Redeemable convertible preference shares, shares authorized		5,611,111
Redeemable convertible preference shares, shares issued		5,611,107
Redeemable convertible preference shares, shares outstanding		5,611,107
Initial Liquidation Preference		$ 10,100
Series B Redeemable convertible preference shares [Member]
Redeemable convertible preference shares, par value		$ 0.00045
Redeemable convertible preference shares, shares authorized		3,665,550
Redeemable convertible preference shares, shares issued		3,629,253
Redeemable convertible preference shares, shares outstanding		3,629,253
Initial Liquidation Preference		13,000
Series C Redeemable convertible preference shares [Member]
Redeemable convertible preference shares, par value		$ 0.00045
Redeemable convertible preference shares, shares authorized		3,027,777
Redeemable convertible preference shares, shares issued		3,027,771
Redeemable convertible preference shares, shares outstanding		3,027,771
Initial Liquidation Preference		16,350
Series D Redeemable convertible preference shares [Member]
Redeemable convertible preference shares, par value		$ 0.00045
Redeemable convertible preference shares, shares authorized		2,222,222
Redeemable convertible preference shares, shares issued		1,047,596
Redeemable convertible preference shares, shares outstanding		1,047,596
Initial Liquidation Preference		$ 11,785

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Revenue	$ 121,066	$ 97,257	$ 94,739
Cost of revenue	40,405	32,458	34,500
Gross profit	80,661	64,799	60,239
Operating expenses:
Research and development	42,829	37,618	34,449
Selling, general and administrative	17,926	15,926	10,313
Total operating expenses	60,755	53,544	44,762
Income from operations	19,906	11,255	15,477
Other income (loss), net	136	(90)	(47)
Income before income taxes	20,042	11,165	15,430
Provision for income taxes	1,854	1,344	1,501
Net income	$ 18,188	$ 9,821	$ 13,929
Net income per share attributable to ordinary shareholders:
Basic	$ 0.64	$ 0.32	$ 0.54
Diluted	$ 0.60	$ 0.30	$ 0.50
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	13,511,646	7,961,944	7,458,627
Diluted	15,016,986	9,469,820	9,107,073

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERENCE SHARES AND SHAREHOLDERS' EQUITY (DEFICIT) (USD $) In Thousands, except Share data	Total	Redeemable Convertible Preference Shares [Member]	Outstanding Ordinary Shares [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]
Beginning Balance, Amount at Jan. 31, 2010	$ (17,433)	$ 39,273	$ 3	$ 4,093	$ (21,529)
Beginning Balance, Shares at Jan. 31, 2010		12,268,131	7,744,461
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Shares	100,779		100,779
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Amount	140			140
Vesting of early exercised stock options	404			404
Stock-based compensation expense related to stock awards granted to employees and consultants	1,856			1,856
Net income	13,929				13,929
Ending Balance, Amount at Jan. 31, 2011	(1,104)	39,273	3	6,493	(7,600)
Ending Balance, Shares at Jan. 31, 2011		12,268,131	7,845,240
Issuance of preference shares, Shares		1,047,596
Issuance of preference shares, Amount		11,627
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Shares	454,053		454,053
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Amount	824			824
Vesting of early exercised stock options	394			394
Stock-based compensation expense related to stock awards granted to employees and consultants	3,616			3,616
Net excess income tax benefit associated with stock-based compensation	125			125
Repurchase of ordinary shares			(698,424)
Repurchase of ordinary shares, Amount	(7,227)			(7,227)
Net income	9,821				9,821
Ending Balance, Amount at Jan. 31, 2012	6,449	50,900	3	4,225	2,221
Ending Balance, Shares at Jan. 31, 2012		13,315,727	7,600,869
Conversion of redeemable convertible preference shares to ordinary shares		(13,315,727)	13,315,727
Conversion of redeemable convertible preference shares to ordinary shares, Amount	50,900	(50,900)	6	50,894
Issuance of shares in connection with initial public offering, net of issuance cost, Shares			5,804,651
Issuance of shares in connection with initial public offering, net of issuance cost, Amount	30,415		3	30,412
Conversion of preference share warrants to ordinary share warrants	110			110
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Shares	313,827		313,827
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Amount	950			950
Vesting of early exercised stock options	314			314
Stock-based compensation expense related to stock awards granted to employees and consultants	4,999			4,999
Net excess income tax benefit associated with stock-based compensation	7			7
Net income	18,188				18,188
Ending Balance, Amount at Jan. 31, 2013	$ 112,332		$ 12	$ 91,911	$ 20,409
Ending Balance, Shares at Jan. 31, 2013			27,035,074

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Cash flows from operating activities:
Net income	$ 18,188	$ 9,821	$ 13,929
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	737	596	563
Loss on disposal of long-lived assets	4	23	4
Amortization of other intangible assets	270	540	1,040
Stock-based compensation	4,999	3,616	1,856
Net excess income tax benefits associated with stock-based compensation	7	(125)	0
Change in value of warrants	(149)	103	0
Changes in operating assets and liabilities:
Accounts receivable	(10,668)	(656)	260
Inventories	(2,132)	624	(5,731)
Prepaid expenses and other current assets	(1,134)	(511)	(27)
Deferred tax assets	(871)	(149)	486
Other assets	(443)	(113)	(227)
Accounts payable	193	(244)	1,575
Accrued liabilities	6,508	1,336	(322)
Income taxes payable	(244)	244	155
Deferred revenue	(4,751)	(2,419)	(536)
Net cash provided by operating activities	10,514	12,686	13,025
Cash flows from investing activities:
Restricted Cash	514	(274)	(243)
Short-term investment	0	0	5,000
Investment in a private company	0	102	(972)
Purchase of property and equipment	(1,528)	(682)	(896)
Purchase of intangible assets	0	(630)	(830)
Net cash provided by (used in) investing activities	(1,014)	(1,484)	2,059
Cash flows from financing activities:
Net proceeds from issuance of preference shares	0	11,627	0
Repurchase of ordinary shares, at cost	0	(7,228)	0
Net proceeds from exercise, repurchase of stock options and employee stock purchase plan	1,610	1,322	213
Proceeds from initial public offering, net of underwriting discounts and commissions and offering costs	30,440	0	0
Net excess income tax benefits associated with stock-based compensation	0	125	0
Net cash provided by financing activities	32,050	5,846	213
Net increase in cash and cash equivalents	41,550	17,048	15,297
Cash and cash equivalents at beginning of period	58,944	41,896	26,599
Cash and cash equivalents at end of period	100,494	58,944	41,896
Supplemental disclosure of cash flow information:
Cash paid for income taxes	3,402	854	657
Supplemental disclosure of noncash investing activities:
Increase in accrued liabilities related to non-monetary assets purchases	122	59	125
Supplemental disclosure of noncash financing activities:
Increase in accrued liabilities related to non-monetary financing activities	25	0	0
Conversion of convertible preference shares to ordinary shares	50,900	0	0
Conversion of convertible preference share warrants to ordinary share warrants	$ 110	$ 0	$ 0

Organization and Summary of Significant Accounting Policies

12 Months Ended

Jan. 31, 2013

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.

On October 15, 2012, in connection with its initial public offering, or IPO, the Company completed the sale of 6,000,000 ordinary shares inclusive of 1,095,349 shares sold by certain shareholders of the Company. The public offering price of the shares sold in this offering was $6.00 per share. The net proceeds from the offering to the Company were approximately $25.4 million after deducting underwriting discounts and commissions and other offering expenses. Upon the completion of the IPO, all 13,315,727 outstanding redeemable convertible preference shares converted into ordinary shares on a one-to-one basis and all outstanding warrants to purchase redeemable convertible preference shares converted into warrants to purchase ordinary shares. On November 6, 2012, a total of 900,000 ordinary shares were sold to the Company’s IPO underwriters in connection with their exercise of the over-allotment option. The net proceeds to the Company from the sale of these shares were approximately $5.0 million after deducting underwriting discounts and commissions.

Basis of Consolidation

The Company’s fiscal year ends on January 31. The consolidated financial statements of the Company and its subsidiaries have been prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”). All intercompany transactions and balances have been eliminated in consolidation.

Use of Estimates

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

On an ongoing basis, management evaluates its estimates and assumptions, including those related to (i) the collectability of accounts receivable; (ii) write downs for excess and obsolete inventories; (iii) the estimated useful lives of long-lived assets; (iv) impairment of long-lived assets and financial instruments; (v) warranty obligations; (vi) the valuation of equity instruments; (vii) the realization of tax assets and estimates of tax liabilities, including reserves for uncertain tax positions; and (viii) the recognition and disclosure of contingent liabilities. These estimates and assumptions are based on historical experience and on various other factors which the Company believes to be reasonable under the circumstances. The company may engage third-party valuation specialists to assist with estimates related to the valuation of financial instruments and assets associated with various contractual arrangements, and the valuation of preference and ordinary shares. Such estimates often require the selection of appropriate valuation methodologies and significant judgment. Actual results could differ from these estimates under different assumptions or circumstances.

Concentration of Risk

The Company’s products are manufactured, assembled and tested by third-party contractors located primarily in Asia. The Company does not have long-term agreements with these contractors. A significant disruption in the operations of one or more of these contractors would impact the production of the Company’s products which could have a material adverse effect on its business, financial condition and results of operations.

A substantial portion of the Company’s revenue is derived from sales through its logistics provider, Wintech Microelectronics Co., Ltd., or Wintech, which serves as its non-exclusive sales representative in all of Asia other than Japan, and to one large direct ODM customer, Chicony Electronics Co., Ltd., or Chicony. Termination of the relationship 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 13 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.

The Company performs ongoing credit evaluations of each of its customers and adjusts credit limits based upon payment history and the customer’s credit worthiness. The Company regularly monitors collections and payments from its customers.

Foreign Currency Transactions

The U.S. dollar is the functional currency for the Company and its subsidiaries. Monetary assets and liabilities denominated in non-U.S. currencies are re-measured to U.S. dollars using current exchange rates in effect at the balance sheet date. Nonmonetary assets and liabilities are re-measured to U.S. dollars using historical exchange rates. Monetary and other accounts are re-measured to U.S. dollars using average exchange rates in effect during each period. Gains or losses from foreign currency re-measurement are included in other income (loss), net in the consolidated statements of operations, and, to date, have not been material.

Cash, Cash Equivalents and Short-Term Investments

The Company considers all highly liquid investments with maturities of less than three months at the time of purchase to be cash equivalents. Investments with maturities at the time of acquisition greater than three months are classified as short-term investments as these are considered as available-for-sale in current operations. There were no cash equivalents or short-term investments as of January 31, 2013 and 2012, respectively.

Cost Method Investment

The Company accounts for its investment in a privately held company under the cost method and reports the investment in other assets in the consolidated balance sheets. The Company monitors the carrying value of the investment and records a reduction in carrying value when a decline in value is deemed to be other than temporary. To date, the Company has not recognized any impairment losses related to this investment.

Trade Accounts Receivable and Allowances for Doubtful Accounts

Trade accounts receivable are recorded at the invoiced amount and do not include finance charges. The Company performs ongoing credit evaluation of its customers and generally requires no collateral. The Company assesses the need for allowances for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments by considering factors such as historical collection experience, credit quality, aging of the accounts receivable balances and current economic conditions that may affect a customer’s ability to pay. There were no write-offs of accounts receivable for the fiscal years 2013, 2012 and 2011, respectively. There was no allowance for doubtful accounts recorded as of January 31, 2013 and 2012, respectively.

Fair Market Value of Financial Instruments

The carrying amounts reflected in the consolidated balance sheets for cash, accounts receivable, accounts payable, accrued liabilities and other current liabilities, approximate fair value due to the short-term nature. The fair value of outstanding warrants to purchase redeemable convertible preference shares converted into warrants to purchase ordinary shares is described in Note 8.

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 sold or scrapped. There has been no material inventory loss to date to be recognized.

Property and Equipment

Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful life of three years for computer equipment, computer software, machinery, equipment and furniture and fixture. Leasehold improvements are amortized over the shorter of the lease term or their estimated useful lives. Repairs and maintenance are charged to expense as incurred.

Intangible Assets

Technology licenses purchased from third parties and that can be used in alternative research and development projects are capitalized as intangible assets. Capitalized costs are amortized over an estimated economic useful life under a straight-line method and recorded as research and development expenses.

Impairment of Long-Lived Assets

The Company records long-lived assets at cost and evaluates them for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Events or changes in circumstances that may indicate that an asset is impaired include significant decreases in the market value of an asset, significant underperformance relative to expected historical or projected future results of operations, a change in the extent or manner in which an asset is utilized, significant declines in the estimated fair value of the overall Company for a sustained period, shifts in technology, loss of key management or personnel, changes in the Company’s operating model or strategy and competitive forces. When the sum of the expected future undiscounted cash flows expected to be generated by the related asset group is less than its carrying amount, an impairment loss would be recognized. Should impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset over the asset’s estimated fair value. There has been no occurrence of events to date that would trigger an impairment analysis. As such, no impairment charge has been recognized as of January 31, 2013.

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 consolidated balance sheets. Any price adjustments are recorded as a reduction 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 comprised 2%, 3% and 2% of the Company’s revenue in the fiscal years 2013, 2012 and 2011, 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.

Warranty Costs

The Company typically provides warranty on its products. The Company accrues for the estimated warranty costs at the time when revenue is recognized. The warranty accruals are regularly monitored by management based upon historical experience and any specifically identified failures. While the Company engages in extensive product quality assessment, actual product failure rates, material usage or service delivery costs could differ from estimates and revisions to the estimated warranty liability would be required. The Company’s warranty accruals have not been material to date.

Research and Development

Research and development costs are expensed as incurred and consist primarily of personnel costs, product development costs, which include engineering services, development software and hardware tools, license fees, cost of fabrication of masks for prototype products, other development materials costs, depreciation of equipment used in research and development and allocation of facilities costs.

Selling, General and Administrative

Selling, general and administrative expense consists of personnel costs, travel and trade show costs, legal expenses, other professional services and occupancy costs. Advertising expenses have not been material to date.

Operating Leases

The Company recognizes rent expense on a straight-line basis over the term of the lease. The difference between rent expense and rent paid is recorded as deferred rent and is included in accrued liabilities.

Income Taxes

The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in its financial statements or tax returns. In estimating future tax consequences, generally all expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized.

The Company applies authoritative guidance for the accounting for uncertainty in income taxes. The guidance requires that tax effects of a position be recognized only if it is “more likely than not” to be sustained based solely on its technical merits as of the reporting date. Upon estimating the Company’s tax positions and tax benefits, the Company considered and evaluated numerous factors, which may require periodic adjustments and which may not reflect the final tax liabilities. The Company adjusts its financial statements to reflect only those tax positions that are more likely than not to be sustained under examination.

As part of the process of preparing consolidated financial statements, the Company is required to estimate its taxes in each of the jurisdictions in which it operates. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differing treatment of items, such as accruals and allowances not currently deductible for tax purposes. These differences result in deferred tax assets, which are included in the consolidated balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the consolidated statements of operations become deductible expenses under applicable income tax laws, or loss or credit carryforwards are utilized.

In assessing whether deferred tax assets may be realized, management considers whether it is more likely than not that some portion or all of deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income.

The Company makes estimates and judgments about its future taxable income based on assumptions that are consistent with its plans and estimates. Should the actual amounts differ from estimates, the amount of valuation allowance could be materially impacted. Any adjustment to the deferred tax asset valuation allowance would be recorded in the income statement for the periods in which the adjustment is determined to be required.

Stock-Based Compensation

The Company measures stock-based compensation for equity awards granted to employees and directors based on the estimated fair value on the grant date, and recognizes that compensation as expense using the straight-line attribution method for service condition awards or using the graded-vesting attribution method for awards with performance conditions over the requisite service period, which is typically the vesting period of each award. The Company estimates the fair value of awards of restricted stock units, or RSUs, based on the fair market value of its ordinary shares on the date of grant. The Company uses the Black-Scholes option pricing model to determine the fair value of each option grant. Determining the fair value of stock option awards on the grant date requires the input of various assumptions, including stock price of the underlying ordinary share, the exercise price of the stock option, expected volatility, expected term, risk-free interest rate and dividend rate. The expected term is calculated using the simplified method as prescribed by the guidance provided by the Securities and Exchange Commission, as neither relevant historical experience nor other relevant data are available to estimate future exercise behavior. The expected volatility is based on the historical volatilities of similar companies whose share prices are publicly available for a period commensurate with the expected term. The risk-free interest rate is derived from the average U.S. Treasury constant maturity rates during the respective periods commensurate with the expected term. The expected dividend yield is zero because the Company has not historically paid dividends and has no present intention to pay dividends. The Company uses historical data to estimate pre-vesting award forfeitures and records stock-based compensation only for those awards that are expected to vest. Forfeitures are estimated at the time of grant and revised if necessary in subsequent periods if actual forfeitures differ from estimates.

The Company recognizes non-employee stock-based compensation expense based on the estimated fair value of the equity instrument determined by the Black-Scholes option pricing model. The fair value of the non-employee awards is remeasured at each reporting period until services required under the arrangement are completed, which is the vesting date.

Prior to the initial public offering, or IPO, the Company engaged an independent appraiser to assist in the valuation of its ordinary share price. The board of directors directed these regular valuations and had input into determining the relevant objective and subjective factors accounted for and relevant approaches in each valuation. After the IPO, the exercise price of stock option awards is determined based on the closing price of the Company’s ordinary shares traded on NASDAQ on the grant date.

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 exercise of employee stock purchase plan, upon release of vested restricted stock units, upon conversion of its redeemable convertible preference shares and upon 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 consolidated statements of operations.

Recent Accounting Pronouncements

In May 2011, the FASB issued ASU No. 2011-04—Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS. The FASB amended its guidance to converge fair value measurement and disclosure guidance about fair value measurement under U.S. GAAP with International Financial Reporting Standards (“IFRS”). The amendment changes the wording used to describe many of the requirements in U.S. GAAP for measuring fair value and for disclosing information about fair value measurements. For many of the requirements, the FASB does not intend for the amendment to result in a change in the application of the requirements in the current authoritative guidance. The amendment becomes effective prospectively for the Company’s interim period ending April 30, 2012. The adoption of this amendment did not have a material impact on the Company’s financial position, results of operations or disclosures.

In June 2011, the FASB issued ASU No. 2011-05, Presentation of Comprehensive Income, requiring entities to present comprehensive income in either a single continuous statement or in two separate, but consecutive financial statements. A single statement must present the components of net income, total net income, components of other comprehensive income, total other comprehensive income and a total for comprehensive income. In a two-statement approach, an entity must present the components of net income and total net income in the first statement. That statement must be immediately followed by a financial statement that presents the components of other comprehensive income, a total for other comprehensive income, and a total for comprehensive income. The option to present items of other comprehensive income in the statement of changes in equity is eliminated. The new requirements do not change, under either accounting framework, which components of comprehensive income are recognized in net income or other comprehensive income, or when an item of other comprehensive income must be reclassified to net income. Also, the earnings-per-share computation does not change. The Company adopted this guidance, which did not have an impact on its financial position, results of operations or disclosures and as such, due to the fact that there are no items that impact comprehensive income, no separate statement is presented.

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	1 Months Ended	12 Months Ended
	Nov. 06, 2012	Oct. 15, 2012	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Organization And Summary Of Significant Accounting Policies [Line Items]
Initial public offering of shares		6,000,000
Shares issued during period, shares sold by certain shareholders		1,095,349
Initial public offering price per share		$ 6.00
Proceeds from initial public offering		$ 25.4
Redeemable convertible preference shares converted to ordinary shares		13,315,727
Redeemable convertible preference shares conversion		Converted into ordinary shares on a one-to-one basis
Over-allotment option shares sold	900,000
Net proceeds from the sale of over-allotment shares	$ 5.0
Estimated useful life			3 years	3 years	3 years
Percentage of license revenue to company's revenue			2.00%	3.00%	2.00%
Expected dividend yield			0.00%	0.00%	0.00%

Restricted Cash - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Amount of restricted cash	$ 3	$ 517

Inventories - Schedule of Inventory (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Inventories Net [Line Items]
Work-in-progress	$ 4,044	$ 3,233
Finished goods	4,874	3,553
Total	$ 8,918	$ 6,786

Property and Equipment, net - Schedule of Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Computer equipment and software	$ 2,810	$ 2,481
Machinery and equipment	2,050	1,951
Furniture and fixtures	397	346
Leasehold improvements	642	543
Construction in progress	827	0
Property and equipment, gross	6,726	5,321
Less: accumulated depreciation and amortization	(4,190)	(3,635)
Total property and equipment, net	$ 2,536	$ 1,686

Intangible Assets - Schedule of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 2,400	$ 2,400
Accumulated Amortization	2,400	2,130
Net Carrying Value	$ 0	$ 270

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Accrued Liabilities [Line Items]
Accrued employee compensation	$ 8,599	$ 4,642
Refundable exercised unvested options	210	470
Accrued warranty	352	404
Accrued rebates	272	233
Accrued product development costs	2,875	679
Other accrued liabilities	2,111	1,503
Total accrued liabilities	$ 14,419	$ 7,931

Deferred Revenue and Deferred Cost - Schedule of Deferred Revenue and Related Cost (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Deferred Revenue and Deferred Cost [Line Items]
Deferred revenue on product shipments	$ 3,827	$ 6,968
Deferred revenue from licenses	485	1,955
Deferred cost of revenue on product shipments	(861)	(721)
Total deferred income	$ 3,451	$ 8,202

Capital Stock - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended		12 Months Ended
Capital Stock - Additional Information (Detail) (USD $)	Nov. 06, 2012	Oct. 15, 2012	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011	Oct. 10, 2012
Class of Stock [Line Items]
Net proceeds from issuance of preference shares				$ 0	$ 11,627,000	$ 0
Redeemable convertible preference shares conversion		Converted into ordinary shares on a one-to-one basis
Repurchase of ordinary shares price per share			$ 10.35		$ 10.35
Number of ordinary shares repurchased			698,424		698,424
Cash paid for repurchase of ordinary shares			7,200,000	0	7,228,000	0
Effective date of split				Aug. 24, 2012
Reverse stock split				One (1) ordinary share for every four and one half (4.5) authorized, issued and outstanding ordinary shares and one (1) preference share for every four and one half (4.5) authorized, issued and outstanding preference shares (the "Stock Split").
Initial public offering of shares		6,000,000
Shares issued during period, shares sold by certain shareholders		1,095,349
Initial public offering price per share		$ 6.00
Proceeds from initial public offering		25,400,000
Redeemable convertible preference shares converted to ordinary shares		13,315,727
Over-allotment option shares sold	900,000
Net proceeds from the sale of over-allotment shares	5,000,000
Preference shares, shares authorized		20,000,000	0	20,000,000	0
Preference shares, par value		$ 0.00045	$ 0.00000	$ 0.00045	$ 0.00000
Preference shares, shares issued			0	0	0
Preference shares, shares outstanding			0	0	0
Company issued warrants to purchase Series B redeemable convertible preference shares at an exercise price			3.582	3.582	3.582	3.582
Fair value of the warrants			259,000		259,000
Aggregate fair market value							110,000
Total ordinary share warrants outstanding				36,292
Ordinary shares authorized			44,444,444	200,000,000	44,444,444
Series D Redeemable convertible preference shares [Member]
Class of Stock [Line Items]
Issuance of preference shares			1,047,596
Preference shares, price per share			$ 11.25		$ 11.25
Net proceeds from issuance of preference shares			$ 11,627,000
Redeemable convertible preference shares conversion			Converted into ordinary shares on a one-to-one basis.

Capital Stock - Components of Redeemable Convertible Preference Shares (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	Jan. 31, 2012
Redeemable Convertible Preference Shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, shares authorized	14,526,660
Preference shares, shares outstanding	13,315,727
Initial Liquidation Preference	$ 51,235
Series A Redeemable convertible preference shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	5,611,111
Preference shares, shares outstanding	5,611,107
Initial Liquidation Preference	10,100
Series A Redeemable convertible preference shares [Member] \| Redeemable Convertible Preference Shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	5,611,111
Preference shares, shares outstanding	5,611,107
Initial Liquidation Preference	10,100
Series B Redeemable convertible preference shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	3,665,550
Preference shares, shares outstanding	3,629,253
Initial Liquidation Preference	13,000
Series B Redeemable convertible preference shares [Member] \| Redeemable Convertible Preference Shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	3,665,550
Preference shares, shares outstanding	3,629,253
Initial Liquidation Preference	13,000
Series C Redeemable convertible preference shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	3,027,777
Preference shares, shares outstanding	3,027,771
Initial Liquidation Preference	16,350
Series C Redeemable convertible preference shares [Member] \| Redeemable Convertible Preference Shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	3,027,777
Preference shares, shares outstanding	3,027,771
Initial Liquidation Preference	16,350
Series D Redeemable convertible preference shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	2,222,222
Preference shares, shares outstanding	1,047,596
Initial Liquidation Preference	11,785
Series D Redeemable convertible preference shares [Member] \| Redeemable Convertible Preference Shares [Member]
Convertible Preference Shares [Line Items]
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	2,222,222
Preference shares, shares outstanding	1,047,596
Initial Liquidation Preference	$ 11,785

Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance (Detail)	Jan. 31, 2013	Jan. 31, 2012
Class of Stock [Line Items]
Shares reserved for redeemable convertible preference shares	0	13,315,727
Shares reserved for options and restricted stock units	5,818,126	4,960,843
Shares reserved for employee stock purchase plan	460,445	0
Shares reserved for warrants	36,292	36,292

Employee Benefits and Stock-based Compensation - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Oct. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Voting power of all classes of company's shares		10.00%	10.00%	10.00%
Term of up to 10 years from grant date		10 years	10 years	10 years
Vesting period of stock options		Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months	Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months	Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months
Restricted stock units granted	344,671	345,171
Estimated fair value of restricted stock units, grant date	$ 9.99	$ 9.99
Vesting period of RSUs	1/16th of the RSUs shall vest each 3 months, 100% vest on the fourth anniversary date	1/16th of the RSUs shall vest each 3 months, 100% vest on the fourth anniversary date
Percentage of salary contribution by employees		10.00%
Percentage of purchase price of ordinary shares		85.00%
Unvested early exercised options, repurchased		84,377	76,982
Unvested shares subject to the Company's repurchase rights		53,151	122,064
Amount of income tax benefit recognized on stock-based compensation		$ 507,000	$ 473,000	$ 111,000
Income tax benefit recognized on stock-based compensation which is recorded in paid-in capital		7,000	125,000
Closing price of ordinary shares		$ 9.96
Aggregate intrinsic value of unvested restricted stock units		3,400,000
Non-employee stock-based compensation
Accelerate aggregate stock options			22,222
Additional stock-based compensation			206,000
Unvested stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		7,300,000	9,500,000
Weighted-average period		2 years 3 months 4 days	2 years 8 months 12 days
Unvested restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		$ 2,400,000
Weighted-average period		1 year 9 months 7 days
Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options as percentage of fair market value at grant date		110.00%
Non Statutory Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options as percentage of fair market value at grant date		100.00%

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Income Taxes [Line Items]
U.S. federal income tax rate	34.00%	34.00%	34.00%
Deferred tax liabilities, not recognized	2.9
Cumulative undistributed earnings of foreign subsidiaries	$ 18,400,000
Gross deferred tax assets, net of deferred tax liabilities before valuation allowance	3,598,000	2,768,000
Unrecognized tax benefits	3,018,000	2,213,000	2,007,000	1,883,000
Unrecognized tax benefits that would impact effective tax rate	2,100,000
Income tax liabilities considered as other long term liabilities	1,200,000	1,100,000
Interest expense and penalties related to uncertain tax positions	23,000	37,000	22,000
Interest and penalties related to uncertain tax positions	116,000	93,000
Income taxes payable, including estimated interest and penalties	1,400,000
California state [Member]
Income Taxes [Line Items]
Research and development credit carryforwards	1,800,000
State tax [Member]
Income Taxes [Line Items]
Credit carry forwards for valuation allowance	$ 100,000

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Deferred tax assets:
Deferred revenue		$ 83
Federal and state credits	1,243	1,301
Expenses not currently deductible	1,345	895
Foreign deferred	60	38
Stock-based compensation	950	451
Gross deferred tax assets	3,598	2,768
Valuation allowance	(1,243)	(1,301)
Total deferred tax assets	2,355	1,467
Deferred tax liabilities
Property and equipment	(197)	(180)
Net deferred tax assets	$ 2,158	$ 1,287

Commitments and Contingencies - Future Annual Minimum Lease Payments (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013
Operating Leases Future Minimum Payments Due [Line Items]
2014	$ 3,085
2015	614
2016	391
2017	10
2018	10
Total future annual minimum lease payments	$ 4,110

Related-Party Transactions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2013 Installment	Jan. 31, 2012 Installment	Jan. 31, 2011
Related Party Transaction [Line Items]
Percentage of entity's voting stock owned by related party	10.00%
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Number of quarterly payments	12	17
Total commitment payment of license	$ 5.1
Payment for license agreements	1.8	1.9	0.9
Operating lease expense related to license agreements included in research and development cost	1.8	1.6	0.6
Shareholder [Member]
Related Party Transaction [Line Items]
Percentage of investor own voting stock	4.60%	7.40%
Recognized revenue from related party	76.5	77.6	85.7
Account receivables from related party	$ 8.2	$ 7.8

Subsequent Events - Additional Information (Detail) (Subsequent Events [Member])	1 Months Ended
	Mar. 31, 2013 sqft
Subsequent Events [Member]
Subsequent Event [Line Items]
Lease agreement, square feet	35,000
Lease agreement, term	5 years
Lease agreement terminate year	2019

Subsequent Events - Schedule of Minimum Lease Payments (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Apr. 04, 2013 Subsequent Events [Member]
2014	$ 3,085	$ 530
2015	614	885
2016	391	906
2017	10	927
2018	10	948
Total future annual minimum lease payments	$ 4,110	$ 4,196