Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Cash flows from operating activities:
Net income	$ 50,571	$ 25,654	$ 18,188
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	1,335	1,096	737
Amortization/accretion of marketable securities	675
Loss on disposal of long-lived assets	21	13	4
Amortization of other intangible assets			270
Stock-based compensation	15,692	8,535	4,999
Excess income tax benefits associated with stock-based compensation	(3,286)	(903)	7
Other non-cash items, net	26		(149)
Changes in operating assets and liabilities:
Accounts receivable	(21,343)	1,316	(10,668)
Inventories	(11,241)	(1,534)	(2,132)
Prepaid expenses and other current assets	(563)	(375)	(1,134)
Deferred tax assets	(3,193)	(433)	(871)
Other assets	307	63	(443)
Accounts payable	12,715	1,270	45
Accrued liabilities	6,686	(2,539)	6,656
Income taxes payable	3,490	807	(244)
Deferred tax liabilities	92
Deferred revenue	274	1,380	(4,751)
Net cash provided by operating activities	52,258	34,350	10,514
Cash flows from investing activities:
Investment in a private company	(290)
Purchase of investments	(59,807)
Sales of investments	8,729
Maturities of investments	12,668
Net proceeds from disposal of fixed assets		13
Purchase of property and equipment	(1,361)	(1,701)	(1,528)
Restricted Cash			514
Net cash used in investing activities	(40,061)	(1,688)	(1,014)
Cash flows from financing activities:
Proceeds from exercise of stock options, warrants, and employee stock purchase plan, net of repurchase of stock options	11,414	9,360	1,610
Payment for initial public offering cost		(25)	(1,950)
Proceeds from initial public offering, net of underwriting discounts and commissions			32,390
Excess income tax benefits associated with stock-based compensation	3,286	903
Net cash provided by financing activities	14,700	10,238	32,050
Net increase in cash and cash equivalents	26,897	42,900	41,550
Cash and cash equivalents at beginning of period	143,394	100,494	58,944
Cash and cash equivalents at end of period	170,291	143,394	100,494
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,069	1,766	3,402
Supplemental disclosure of noncash investing activities:
Increase in accrued liabilities related to non-monetary assets purchases	75	24	122
Supplemental disclosure of noncash financing activities:
Increase in accrued liabilities related to non-monetary financing activities			25
Conversion of redeemable convertible preference shares to ordinary shares			50,900
Conversion of redeemable convertible preference share warrants to ordinary share warrants			$ 110