Document and Entity Information	9 Months Ended
Document and Entity Information	Oct. 31, 2012
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Oct. 31, 2012
Document Fiscal Year Focus	2013
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	26,093,016

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Current assets:
Cash	$ 94,820	$ 58,944
Accounts receivable, net	18,243	9,485
Inventories	9,141	6,786
Restricted cash	270	517
Deferred tax assets, current	1,333	861
Prepaid expenses and other current assets	1,516	1,226
Total current assets	125,323	77,819
Property and equipment, net	2,283	1,686
Deferred tax assets, non-current	426	426
Intangible assets, net		270
Other assets	1,520	1,538
Total assets	129,552	81,739
Current liabilities:
Accounts payable	9,345	6,481
Accrued liabilities	12,591	7,931
Income taxes payable	1,115	530
Deferred revenue, current	3,412	8,002
Total current liabilities	26,463	22,944
Deferred revenue, non-current		200
Other long-term liabilities	1,115	1,246
Total liabilities	27,578	24,390
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		50,900
Shareholders' equity:
Preference shares, $0.00045 par value per share, 20,000,000 shares authorized and no shares issued and outstanding at October 31, 2012; no shares authorized, issued and outstanding at January 31, 2012;
Ordinary shares, $0.00045 par value per share, 200,000,000 and 44,444,444 shares authorized at October 31, 2012 and at January 31, 2012, respectively; 26,093,016 shares issued and outstanding at October 31, 2012; 7,600,869 shares issued and outstanding at January 31, 2012	12	3
Additional paid-in capital	85,196	4,225
Retained earnings	16,766	2,221
Total shareholders' equity	101,974	6,449
Total liabilities, redeemable convertible preference shares and shareholders' equity	$ 129,552	$ 81,739

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Preference shares, par value	$ 0.00045
Preference shares, shares authorized	20,000,000
Preference shares, shares issued
Preference shares, shares outstanding
Ordinary shares, par value	$ 0.00045	$ 0.00045
Ordinary shares, shares authorized	200,000,000	44,444,444
Ordinary shares, shares issued	26,093,016	7,600,869
Ordinary shares, shares outstanding	26,093,016	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

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Revenue	$ 35,669	$ 28,778	$ 89,548	$ 72,686
Cost of revenue	12,679	10,093	28,821	24,656
Gross profit	22,990	18,685	60,727	48,030
Operating expenses:
Research and development	10,802	9,169	31,631	27,611
Selling, general and administrative	4,603	3,806	12,812	11,261
Total operating expenses	15,405	12,975	44,443	38,872
Income from operations	7,585	5,710	16,284	9,158
Other income (loss), net	137	3	139	(21)
Income before income taxes	7,722	5,713	16,423	9,137
Provision for income taxes	1,005	665	1,878	1,093
Net income	$ 6,717	$ 5,048	$ 14,545	$ 8,044
Net income per share attributable to ordinary shareholders:
Basic	$ 0.27	$ 0.21	$ 0.55	$ 0.28
Diluted	$ 0.25	$ 0.19	$ 0.51	$ 0.26
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	12,068,819	8,046,362	9,049,864	7,946,206
Diluted	13,415,091	9,513,055	10,506,293	9,465,640

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Oct. 31, 2012	Oct. 31, 2011
Cash flows from operating activities:
Net income	$ 14,545	$ 8,044
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	545	444
Loss on disposal of long-lived assets	2	15
Amortization of other intangible assets	270	405
Stock-based compensation	3,441	2,645
Change in value of warrants	(149)	53
Changes in operating assets and liabilities:
Accounts receivable	(8,758)	(953)
Inventories	(2,355)	(2,515)
Prepaid expenses and other current assets	(290)	(1,311)
Deferred tax assets	(472)	4
Other assets	17	(34)
Accounts payable	2,259	(2,158)
Accrued liabilities	4,202	2,465
Income taxes payable	585	340
Deferred revenue	(4,790)	(1,705)
Net cash provided by operating activities	9,052	5,739
Cash flows from investing activities:
Restricted Cash	247	(268)
Proceeds from sale of shares in a private company		102
Purchase of property and equipment	(997)	(440)
Purchase of intangible assets		(630)
Net cash used in investing activities	(750)	(1,236)
Cash flows from financing activities:
Net proceeds from exercise and repurchase of stock options	933	1,177
Proceeds from initial public offering, net of underwriting discounts and commissions and offering costs	26,641
Net cash provided by financing activities	27,574	1,177
Net increase in cash and cash equivalents	35,876	5,680
Cash and cash equivalents at beginning of period	58,944	41,896
Cash and cash equivalents at end of period	94,820	47,576
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,897	755
Supplemental disclosure of noncash investing activities:
Increase in accrued liabilities related to non-monetary assets purchases	147	43
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 Significant Accounting Policies

9 Months Ended

Oct. 31, 2012

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.

Effective August 24, 2012, the Company’s board of directors and shareholders approved a reverse stock split of 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”). Upon approval of the Stock Split, the ordinary shares and preference shares outstanding and the number of ordinary shares and preference shares covered by each outstanding right, option, warrant or arrangement were proportionately decreased to reflect the Stock Split and the exercise or purchase price of each such right, option, warrant or arrangement was proportionately increased to reflect the Stock Split. The Company is authorized to accept the surrender of fractional shares resulting from the Stock Split from any shareholder that elects to forego payment for such fractional shares.

On October 15, 2012, the Company closed its initial public offering, or IPO, 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 the offering was $6.00 per share. The net proceeds from the offering to the Company were $25.4 million after deducting underwriting discounts and commissions and other offering expenses. Upon the closing of the IPO, all outstanding convertible preference shares converted into ordinary shares on a one-to-one basis and all outstanding warrants to purchase convertible preference shares converted into warrants to purchase ordinary shares.

Basis of presentation

In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring items, necessary for a fair statement of the Company’s financial statements for interim periods in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s final prospectus (“Prospectus”) filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended with the U.S. Securities and Exchange Commission on October 10, 2012. The accounting policies are described in the “ Notes to Consolidated Financial Statements ” in the Prospectus 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 U.S. GAAP. The results of operations for the three and nine months ended October 31, 2012 are not necessarily indicative of the operating results for the full year or for any other subsequent interim period.

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 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 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. Actual results could differ from those estimates.

On an ongoing basis, management evaluates its estimates and assumptions, including those related to (i) the collectability of accounts receivable; (ii) write down for excess and obsolete inventories; (iii) the estimated useful lives of long-lived assets; (iv) impairment of long-lived assets and financial instruments; (v) warranty obligations; (vi) the valuation of equity instruments; (vii) the realization of tax assets and estimates of tax liabilities and tax reserves; 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, which serves as its non-exclusive sales representative in all of Asia other than Japan, and through one direct ODM customer. 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, cash equivalents, restricted 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 or cash equivalents. 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 condensed 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. There were no cash equivalents and short-term investments as of October 31, 2012 and January 31, 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 non-current assets. 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 nine months ended October 31, 2012 and 2011, respectively. There was no allowance for doubtful accounts recorded as of October 31, 2012 and January 31, 2012, respectively.

Fair Market Value of Financial Instruments

The carrying amount reflected in the balance sheet for cash, accounts receivable, accounts payable, accrued expenses and other current liabilities, approximate fair value due to the short-term nature of these financial instruments. The fair market value of outstanding warrants to purchase redeemable convertible preference 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.

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 and equipment. 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 which 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. To date, the Company has not recognized any impairment losses related to long-lived assets.

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 goods 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 with 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 upon shipment as persuasive evidence of the arrangement exists, legal title to the products has transferred, the fee is fixed and collection of the resulting receivable is reasonably assured. 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 support period in accordance with ASC 985, Software Revenue Recognition. The revenue from those licenses comprised 1% and 3% of the Company’s revenue for the three months ended October 31, 2012 and 2011, respectively. The revenue from those licenses comprised 2% and 3% of the Company’s revenue for the nine months ended October 31, 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 accrual has 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 salaries, stock-based compensation, employee benefits, travel and trade show costs, legal, finance and human resources personnel. In addition, these expenses include fees for 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 expenses.

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 made 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 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-based 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 was 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 entities whose share prices are publicly available. 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 option forfeitures and records stock-based compensation only for those options 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.

Net Income (Loss) Per Ordinary Share

The Company applies the two-class method to calculate and present net income (loss) 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 (loss) per share is computed by dividing net income (loss) allocable to ordinary shares by the weighted-average number of ordinary shares outstanding for the period. Diluted net income (loss) per share is computed by dividing net income (loss) 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 conversion of its redeemable convertible preference shares and upon exercise of warrants.

Effective April 1, 2009, the Company adopted the new accounting guidance for determining whether instruments granted in stock-based payment transactions are participating securities. The guidance clarified that 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 share. The net income per share data presented for all prior periods has been prepared to conform to the provisions of this accounting guidance.

Comprehensive Income (Loss)

There are no differences between comprehensive income or loss as defined by ASC 220, Comprehensive Income, and net income or loss as reported in the Company’s statement 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, no separate statement is presented.

Subsequent Events	9 Months Ended
Subsequent Events	Oct. 31, 2012
Subsequent Events	15. Subsequent Events 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.

Restricted Cash - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Amount of Restricted Cash	$ 270	$ 517

Inventories - Inventory (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Inventories Net [Line Items]
Work-in-progress	$ 4,258	$ 3,233
Finished goods	4,883	3,553
Total	$ 9,141	$ 6,786

Property and Equipment, Net - Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Computer equipment and software	$ 2,845	$ 2,481
Machinery and equipment	2,017	1,951
Furniture and fixtures	395	346
Leasehold improvements	630	543
Construction in progress	547
Property, Plant and Equipment, Gross, Total	6,434	5,321
Less: accumulated depreciation and amortization	(4,151)	(3,635)
Total property and equipment, net	$ 2,283	$ 1,686

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

Accrued Liabilities - Accrued Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Accrued Liabilities [Line Items]
Accrued employee compensation	$ 6,900	$ 4,642
Refundable exercised unvested option	268	470
Accrued warranty	356	404
Accrued rebates	251	233
Accrued product development costs	1,798	679
Other accrued liabilities	3,018	1,503
Total accrued liabilities	$ 12,591	$ 7,931

Deferred Revenue and Deferred Cost - Deferred Revenue and Related Cost (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Deferred Revenue and Deferred Cost [Line Items]
Deferred revenue on product shipments	$ 3,132	$ 6,968
Deferred revenue from licenses	942	1,955
Deferred cost of revenue on product shipments	(662)	(721)
Total deferred income	$ 3,412	$ 8,202

Capital Stock - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended
Capital Stock - Additional Information (Detail) (USD $)	Oct. 10, 2012	Oct. 31, 2012	Jan. 31, 2012
Class of Stock [Line Items]
Outstanding redeemable convertible preference shares	13,315,727
Redeemable convertible preference shares conversion	Converted into ordinary shares on a one-to-one basis
Preference shares, shares authorized		20,000,000
Preference shares, par value		$ 0.00045
Preference shares, shares issued
Preference shares, shares outstanding
Company issued warrants to purchase Series B redeemable convertible preference shares at an exercise price			3.582
Total preference share warrants outstanding			36,292
Fair value of the warrants			$ 259,000
Fair market value	$ 110,000
Total ordinary share warrants outstanding		36,292
Ordinary shares authorized		200,000,000	44,444,444
After IPO [Member]
Class of Stock [Line Items]
Outstanding redeemable convertible preference shares

Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance (Detail)	Oct. 31, 2012	Jan. 31, 2012
Class of Stock [Line Items]
Shares reserved for redeemable convertible preference shares		13,315,727
Shares reserved for options and restricted stock units	5,823,889	4,924,551
Shares reserved for employee stock purchase plan	460,445
Shares reserved for warrants	36,292	36,292

Employee Benefits and Stock-Based Compensation - Stock Option Activities (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Oct. 31, 2012	Jan. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares	4,375,906
Granted, Shares	385,206
Exercised, Shares	(271,769)
Forfeited, Shares	(129,238)
Outstanding, Shares	4,360,105
Exercisable, Shares	3,005,705
Vested and expected to vest, Shares	4,285,956
Granted, Weighted average exercise price	$ 8.75
Exercised, Weighted average exercise price	$ 3.43
Forfeited, Weighted average exercise price	$ 7.00
Outstanding , Weighted average exercise price	$ 6.00	$ 5.63
Exercisable , Weighted average exercise price	$ 5.03
Vested and expected to vest, Weighted average exercise price	$ 5.96
Granted, Weighted Average Grant Date Fair Value	$ 5.21
Exercised, Total Intrinsic Value of options Exercised	$ 1,776
Outstanding , Weighted Average Remaining Contractual Term	6 years 11 months 23 days
Exercisable , Weighted Average Remaining Contractual Term	6 years 3 months 26 days
Vested and expected to vest, Weighted Average Remaining Contractual Term	6 years 11 months 12 days
Outstanding , aggregate intrinsic value	9,055
Exercisable , aggregate intrinsic value	8,371
Vested and expected to vest , aggregate intrinsic value	$ 9,015

Employee Benefits and Stock-Based Compensation - Stock Options Outstanding and Exercisable (Detail) (USD $)	9 Months Ended
	Oct. 31, 2012	Jan. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	4,360,105	4,375,906
Range of Exercise Prices, Weighted Average Remaining Contractual Life	6 years 11 months 23 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 6.00	$ 5.63
Range of Exercise Prices, Shares Exercisable	3,005,705
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 5.03
Exercise Price Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	94,443
Range of Exercise Prices, Weighted Average Remaining Contractual Life	1 year 9 months 4 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 0.23
Range of Exercise Prices, Shares Exercisable	94,443
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 0.23
Range of Exercise Prices, Lower	$ 0.18
Range of Exercise Prices, Upper	$ 0.36
Exercise Price Range Two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	41,912
Range of Exercise Prices, Weighted Average Remaining Contractual Life	3 years 6 months 29 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 0.63
Range of Exercise Prices, Shares Exercisable	41,912
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 0.63
Range of Exercise Prices, Lower	$ 0.37
Range of Exercise Prices, Upper	$ 0.63
Exercise Price Range Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	467,393
Range of Exercise Prices, Weighted Average Remaining Contractual Life	4 years 5 months 1 day
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 1.21
Range of Exercise Prices, Shares Exercisable	467,393
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 1.21
Range of Exercise Prices, Lower	$ 0.64
Range of Exercise Prices, Upper	$ 1.22
Exercise Price Range Four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	1,198,042
Range of Exercise Prices, Weighted Average Remaining Contractual Life	6 years 15 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 3.04
Range of Exercise Prices, Shares Exercisable	1,067,812
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 3.03
Range of Exercise Prices, Lower	$ 1.23
Range of Exercise Prices, Upper	$ 3.20
Exercise Price Range Five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	390,028
Range of Exercise Prices, Weighted Average Remaining Contractual Life	7 years 1 month 17 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 6.43
Range of Exercise Prices, Shares Exercisable	243,200
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 6.61
Range of Exercise Prices, Lower	$ 3.21
Range of Exercise Prices, Upper	$ 6.62
Exercise Price Range Six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Shares Outstanding	2,168,287
Range of Exercise Prices, Weighted Average Remaining Contractual Life	8 years 3 months 22 days
Range of Exercise Prices, Stock Options Outstanding, Weighted Average Exercise Price	$ 8.94
Range of Exercise Prices, Shares Exercisable	1,090,945
Range of Exercise Prices, Stock Options Exercisable, Weighted Average Exercise Price	$ 8.86
Range of Exercise Prices, Lower	$ 6.63
Range of Exercise Prices, Upper	$ 9.99

Employee Benefits and Stock-based Compensation - Restricted Stock Units Activities (Detail) (USD $)	9 Months Ended
	Oct. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance shares
Granted, shares	344,671
Vested, shares
Forfeited, shares	(1,687)
Unvested, ending balance shares	342,984
Unvested beginning balance, Weighted-Average Grant-Date Fair Value
Granted, Weighted-Average Grant-Date Fair Value	$ 9.99
Vested, Weighted-Average Grant-Date Fair Value
Forfeited, Weighted-Average Grant-Date Fair Value	$ 9.99
Unvested ending balance, Weighted-Average Grant-Date Fair Value	$ 9.99

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Income Taxes [Line Items]
Income tax expense	$ 1,005,000	$ 665,000	$ 1,878,000	$ 1,093,000
Estimated effective tax rate	13.00%	11.60%	11.40%	12.00%
Unrecognized tax benefit	$ 2,300,000		$ 2,300,000

Commitments and Contingencies - Future Annual Minimum Lease Payments (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012
Operating Leases Future Minimum Payments Due [Line Items]
2013	$ 1,171
2014	2,877
2015	572
2016	390
2017	10
Total future annual minimum lease payments	$ 5,020

Subsequent Events - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		0 Months Ended
	Oct. 31, 2012	Jan. 31, 2012	Nov. 06, 2012 Subsequent Events [Member]
Subsequent Event [Line Items]
Over-allotment shares sold	26,093,016	7,600,869	900,000
Net proceeds from the sale of over-allotment shares	$ 26,641		$ 5,000