Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Cash flows from operating activities
Net income	$ 96,959	$ 82,245	$ 277,080	$ 234,936
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,525	3,845	22,720	11,626
Reduction of operating lease right-of-use assets	3,322	1,798	9,411	5,016
Accretion of discount on short-term investments	1,203	(722)	1,688	(2,996)
Stock-based compensation	48,973	29,321	135,246	78,447
Amortization of deferred costs	5,350	4,832	15,425	14,524
Deferred income taxes	(1,894)	432	(3,532)	1,771
Loss (Gain) on foreign currency from mark-to-market derivative	19	(74)	14	(112)
Bad debt (recovery) expense	(181)	270	(60)	(42)
Changes in operating assets and liabilities:
Accounts receivable	37,448	28,319	206,214	186,633
Unbilled accounts receivable	(16,585)	(9,515)	(20,418)	(12,777)
Deferred costs	(6,177)	(4,500)	(15,312)	(13,528)
Income taxes payable	4,538	3,909	(453)	4,858
Prepaid expenses and other current and long-term assets	8,195	5,610	(2,937)	1,513
Accounts payable	3,060	1,253	(456)	1,216
Accrued expenses and other current liabilities	1,541	(1,682)	4,357	231
Deferred revenue	(90,291)	(78,326)	(137,980)	(105,637)
Operating lease liabilities	(3,229)	(1,625)	(8,496)	(5,143)
Other long-term liabilities	(4,373)	(3,886)	384	(2,270)
Net cash provided by operating activities	95,403	61,504	482,895	398,266
Cash flows from investing activities
Purchases of short-term investments	(417,898)	(190,695)	(874,465)	(628,784)
Maturities and sales of short-term investments	158,628	194,661	528,194	571,398
Long-term assets	(3,316)	(1,237)	(8,456)	(4,228)
Net cash (used in) provided by investing activities	(262,586)	2,729	(354,727)	(61,614)
Cash flows from financing activities
Changes in lease liabilities - finance leases	79	(241)	(420)	(729)
Proceeds from exercise of common stock options	6,186	1,607	25,245	8,618
Net cash provided by financing activities	6,265	1,366	24,825	7,889
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(599)	(487)	2,683	(2,931)
Net change in cash, cash equivalents, and restricted cash	(161,517)	65,112	155,676	341,610
Cash, cash equivalents, and restricted cash at beginning of period	796,990	828,676	479,797	552,178
Cash, cash equivalents, and restricted cash at end of period	635,473	893,788	635,473	893,788
Cash, cash equivalents, and restricted cash at end of period:
Cash, cash equivalents, and restricted cash at end of period	635,473	893,788	635,473	893,788
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	2,198	1,739	17,153	5,004
Excess tax benefits from employee stock plans	17,329	8,931	59,067	39,509
Non-cash investing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases	$ 697	$ 109	$ 1,471	$ (428)