Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Income Statement [Abstract]
Revenue	$ 218,278us-gaap_Revenues	$ 157,608us-gaap_Revenues	$ 121,066us-gaap_Revenues
Cost of revenue	79,142us-gaap_CostOfRevenue	57,761us-gaap_CostOfRevenue	40,405us-gaap_CostOfRevenue
Gross profit	139,136us-gaap_GrossProfit	99,847us-gaap_GrossProfit	80,661us-gaap_GrossProfit
Operating expenses:
Research and development	57,978us-gaap_ResearchAndDevelopmentExpense	48,777us-gaap_ResearchAndDevelopmentExpense	42,829us-gaap_ResearchAndDevelopmentExpense
Selling, general and administrative	29,297	23,153	17,926
Total operating expenses	87,275us-gaap_OperatingExpenses	71,930us-gaap_OperatingExpenses	60,755us-gaap_OperatingExpenses
Income from operations	51,861us-gaap_OperatingIncomeLoss	27,917us-gaap_OperatingIncomeLoss	19,906us-gaap_OperatingIncomeLoss
Other income (loss), net	175us-gaap_NonoperatingIncomeExpense	(22)us-gaap_NonoperatingIncomeExpense	136us-gaap_NonoperatingIncomeExpense
Income before income taxes	52,036	27,895	20,042
Provision for income taxes	1,465us-gaap_IncomeTaxExpenseBenefit	2,241us-gaap_IncomeTaxExpenseBenefit	1,854us-gaap_IncomeTaxExpenseBenefit
Net income	$ 50,571us-gaap_NetIncomeLoss	$ 25,654us-gaap_NetIncomeLoss	$ 18,188us-gaap_NetIncomeLoss
Net income per share attributable to ordinary shareholders:
Basic	$ 1.70us-gaap_EarningsPerShareBasic	$ 0.93us-gaap_EarningsPerShareBasic	$ 0.64us-gaap_EarningsPerShareBasic
Diluted	$ 1.57us-gaap_EarningsPerShareDiluted	$ 0.85us-gaap_EarningsPerShareDiluted	$ 0.60us-gaap_EarningsPerShareDiluted
Weighted-average shares used to compute net income per share attributable to ordinary shareholders:
Basic	29,742,653	27,680,778	13,511,646
Diluted	32,278,127	30,172,563	15,016,986

The aggregate cost of goods produced and sold and services rendered during the reporting period.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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