Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ (44,792)	$ (30,447)	$ 18,852
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	11,631	7,221	4,770
Amortization/accretion of marketable debt securities	(969)	(670)	172
Stock-based compensation	66,871	60,812	56,861
Deferred income taxes	187	(6,945)	2,092
Other non-cash items, net	(71)	350	165
Changes in operating assets and liabilities:
Accounts receivable	7,725	5,082	7,302
Inventories	(4,719)	5,131	(3,238)
Prepaid expenses and other current assets	1,057	(2,202)	379
Other non-current assets	(3,298)	(155)	(33)
Accounts payable	2,109	(7,014)	(140)
Accrued liabilities	5,079	(8,302)	1,430
Income taxes payable	(302)	57	368
Deferred revenue	172	265	(7,026)
Lease liabilities	(2,851)	0	0
Other long-term liabilities	1,585	1,289	3,450
Net cash provided by operating activities	39,414	24,472	85,404
Cash flows from investing activities:
Purchase of investments	(225,913)	(207,841)	(74,863)
Sales of investments	96,363	66,211	10,900
Maturities of investments	122,795	65,428	58,050
Purchase of property and equipment	(1,821)	(2,940)	(3,687)
Net cash used in investing activities	(8,576)	(79,142)	(9,600)
Cash flows from financing activities:
Proceeds from exercise of stock options and employee stock purchase plan	11,960	6,686	7,091
Stock repurchase	0	(99,904)	(54,788)
Payment for intangible assets	(5,444)	(4,735)	(4,306)
Net cash provided by (used in) financing activities	6,516	(97,953)	(52,003)
Net increase (decrease) in cash, cash equivalents and restricted cash	37,354	(152,623)	23,801
Cash, cash equivalents and restricted cash at beginning of period	194,058	346,681	322,880
Cash, cash equivalents and restricted cash at end of period	231,412	194,058	346,681
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,811	1,409	845
Supplemental disclosure of noncash investing activities:
Unpaid liabilities related to intangible and fixed assets purchases	$ 12,284	$ 933	$ 9,008