Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Cash flows from operating activities:
Net loss	$ (59,786)	$ (44,792)	$ (30,447)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	11,967	11,631	7,221
Amortization (accretion) of premium (discount) on marketable debt securities, net	721	(969)	(670)
Stock-based compensation	70,134	66,871	60,812
Deferred income taxes	(514)	187	(6,945)
Other non-cash items, net	65	(71)	350
Changes in operating assets and liabilities:
Accounts receivable	(6,487)	7,725	5,082
Inventories	(3,110)	(4,719)	5,131
Prepaid expenses and other current assets	(537)	1,057	(2,202)
Other non-current assets	1,141	(3,298)	(155)
Accounts payable	6,214	2,109	(7,014)
Accrued and other current liabilities	12,055	5,079	(8,302)
Income taxes payable	272	(302)	57
Deferred revenue	144	172	265
Operating lease liabilities	(2,416)	(2,851)	0
Other long-term liabilities	937	1,585	1,289
Net cash provided by operating activities	30,800	39,414	24,472
Cash flows from investing activities:
Purchases of investments	(219,677)	(225,913)	(207,841)
Sales of investments	70,087	96,363	66,211
Maturities of investments	123,208	122,795	65,428
Purchase of property and equipment	(1,952)	(1,821)	(2,940)
Purchase of intangible assets	(2,990)	0	0
Net cash used in investing activities	(31,324)	(8,576)	(79,142)
Cash flows from financing activities:
Proceeds from exercise of stock options and employee stock purchase plan	16,417	11,960	6,686
Stock repurchase	(1,000)	0	(99,904)
Payment for intangible assets	(5,021)	(5,444)	(4,735)
Net cash provided by (used in) financing activities	10,396	6,516	(97,953)
Net increase (decrease) in cash, cash equivalents and restricted cash	9,872	37,354	(152,623)
Cash, cash equivalents and restricted cash at beginning of period	231,412	194,058	346,681
Cash, cash equivalents and restricted cash at end of period	241,284	231,412	194,058
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,531	1,811	1,409
Supplemental disclosure of noncash investing activities:
Unpaid liabilities related to intangible and fixed assets purchases	$ 4,302	$ 12,284	$ 933