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	$ 301,118	$ 229,832	$ 151,177
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,859	14,071	14,277
Reduction of operating lease right-of-use assets	7,966
Amortization of premiums (accretion of discount) on short-term investments	(3,274)	(2,431)	1,389
Stock-based compensation	115,906	76,425	54,049
Amortization of deferred costs	20,521	18,378	16,647
Deferred income taxes	(6,663)	(8,091)	1,209
(Gain) Loss on foreign currency from market-to-market derivative	(120)	(177)	265
Bad debt expense (recovery)	244	198	(242)
Changes in operating assets and liabilities:
Accounts receivable	(55,531)	(78,995)	(47,799)
Unbilled accounts receivable	(14,555)	(4,774)	(4,329)
Deferred costs	(25,237)	(18,941)	(18,795)
Income taxes payable	1,131	637	(2,520)
Prepaid expenses and other current and long-term assets	(2,700)	(10,562)	(2,493)
Accounts payable	2,813	1,822	1,396
Accrued expenses and other current liabilities	(15,230)	963	7,149
Deferred revenue	97,753	89,416	58,240
Operating lease liabilities	(7,480)
Other long-term liabilities	854	3,056	3,818
Net cash provided by operating activities	437,375	310,827	233,438
Cash flows from investing activities
Purchases of short-term investments	(752,518)	(726,379)	(437,858)
Maturities and sales of short-term investments	688,091	632,329	294,705
Purchases of property and equipment	(3,113)	(8,440)	(9,633)
Acquisitions, net of cash and restricted cash acquired	(448,162)	0	0
Capitalized internal-use software development costs	(1,208)	(1,379)	(1,734)
Net cash used in investing activities	(516,910)	(103,869)	(154,520)
Cash flows from financing activities
Reduction of lease liabilities - finance leases	(984)
Proceeds from exercise of common stock options	10,994	25,910	20,773
Net cash provided by financing activities	10,010	25,910	20,773
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(2,856)	(2,077)	3,089
Net change in cash, cash equivalents, and restricted cash	(72,381)	230,791	102,780
Cash, cash equivalents, and restricted cash at beginning of period	552,178	321,387	218,607
Cash, cash equivalents, and restricted cash at end of period	479,797	552,178	321,387
Cash, cash equivalents, and restricted cash at end of period:
Cash and cash equivalents	476,733	550,971	320,183
Restricted cash included in other long-term assets	3,064	1,207	1,204
Cash, cash equivalents, and restricted cash at end of period	479,797	552,178	321,387
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	14,289	19,541	12,461
Excess tax benefits from employee stock plans	50,411	45,830	45,864
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases	$ 567	$ 644	$ (1,388)