Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ (25,904)	$ 17,591
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of property and equipment	1,901	1,306
Amortization of intangible assets	3,454	2,018
Amortization/accretion of marketable securities	(311)	152
Stock-based compensation	44,937	42,075
Other non-cash items, net	358	93
Changes in operating assets and liabilities:
Accounts receivable	(1,123)	(8,601)
Inventories	55	(952)
Prepaid expenses and other current assets	700	380
Deferred tax assets	(285)	(762)
Other assets	(213)	10
Accounts payable	(8,681)	6,253
Accrued liabilities	(5,192)	(2,460)
Income taxes payable	(181)	1,879
Deferred revenue	140	(2,206)
Other long-term liabilities	843	3,518
Net cash provided by operating activities	10,498	60,294
Cash flows from investing activities:
Purchase of investments	(139,816)	(53,786)
Sales of investments	50,618	8,500
Maturities of investments	40,928	34,460
Purchase of property and equipment	(2,380)	(2,402)
Net cash used in investing activities	(50,650)	(13,228)
Cash flows from financing activities:
Stock repurchase	(96,419)	(51,505)
Proceeds from exercise of stock options and employee stock purchase plan	4,722	4,961
Payment for intangible asset	(2,483)	(2,460)
Net cash used in financing activities	(94,180)	(49,004)
Net decrease in cash, cash equivalents and restricted cash	(134,332)	(1,938)
Cash, cash equivalents and restricted cash at beginning of period	346,681	322,880
Cash, cash equivalents and restricted cash at end of period	212,349	320,942
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,263	762
Supplemental disclosure of noncash investing and financing activities:
Unpaid liabilities related to intangible and fixed assets additions	$ 299	$ 10,731