Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Cash flows from operating activities:
Net income	$ 17,591	$ 39,460
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment	1,306	1,170
Amortization of intangible assets	2,018	36
Amortization/accretion of marketable securities	152	172
Stock-based compensation	42,075	35,474
Other non-cash items, net	92	57
Changes in operating assets and liabilities:
Accounts receivable	(8,601)	(1,986)
Inventories	(952)	(5,173)
Prepaid expenses and other current assets	380	(581)
Deferred tax assets	(762)	604
Other assets	10	(45)
Accounts payable	6,253	14,189
Accrued liabilities	(2,460)	825
Income taxes payable	1,879	572
Deferred tax liabilities	0	(58)
Deferred revenue	(2,206)	(3,192)
Other long-term liabilities	3,518	(476)
Net cash provided by operating activities	60,293	81,048
Cash flows from investing activities:
Purchase of investments	(53,786)	(72,950)
Sales of investments	8,500	28,368
Maturities of investments	34,460	25,560
Purchase of property and equipment	(2,402)	(2,070)
Net cash used in investing activities	(13,228)	(21,092)
Cash flows from financing activities:
Stock repurchase	(51,505)	(20,183)
Proceeds from exercise of stock options and employee stock purchase plan	4,961	5,626
Payment for software license liabilities	(2,460)	0
Net cash used in financing activities	(49,004)	(14,557)
Net increase (decrease) in cash and cash equivalents	(1,939)	45,399
Cash and cash equivalents at beginning of period	322,872	268,056
Cash and cash equivalents at end of period	320,933	313,455
Supplemental disclosure of cash flow information:
Cash paid for income taxes	762	914
Supplemental disclosure of noncash investing and financing activities:
Increase in liabilities related to intangible and fixed asset purchases	$ 10,731	$ 34