Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Cash flows from operating activities
Net income	$ 82,245	$ 64,085	$ 234,936	$ 158,681
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,643	3,383	16,642	10,477
Accretion of discount on short-term investments	(722)	(848)	(2,996)	(1,380)
Stock-based compensation	29,321	19,918	78,447	56,647
Amortization of deferred costs	4,832	4,595	14,524	13,697
Deferred income taxes	432	1,824	1,771	2,642
Gain on foreign currency from mark-to-market derivative	(74)	(19)	(112)	(182)
Bad debt expense (recovery)	270	84	(42)	262
Changes in operating assets and liabilities:
Accounts receivable	28,319	21,658	186,633	134,353
Unbilled accounts receivable	(9,515)	(5,212)	(12,777)	(6,641)
Deferred costs	(4,500)	(4,504)	(13,528)	(11,426)
Income taxes payable	3,909	1,029	4,858	525
Prepaid expenses and other current and long-term assets	5,610	(6,018)	1,513	(9,527)
Accounts payable	1,253	2,982	1,216	3,520
Accrued expenses and other current liabilities	(1,682)	406	231	(3,698)
Deferred revenue	(78,326)	(62,860)	(105,637)	(70,616)
Lease liabilities	(1,625)		(5,143)
Other long-term liabilities	(3,886)	1,053	(2,270)	1,620
Net cash provided by operating activities	61,504	41,556	398,266	278,954
Cash flows from investing activities
Purchases of short-term investments	(190,695)	(214,839)	(628,784)	(589,070)
Maturities and sales of short-term investments	194,661	130,137	571,398	447,947
Purchases of property and equipment	(881)	(4,163)	(3,167)	(5,558)
Capitalized internal-use software development costs	(356)	(495)	(1,061)	(1,009)
Net cash provided by (used in) investing activities	2,729	(89,360)	(61,614)	(147,690)
Cash flows from financing activities
Reduction of lease liabilities - finance leases	(241)		(729)
Proceeds from exercise of common stock options	1,607	4,867	8,618	19,728
Net cash provided by financing activities	1,366	4,867	7,889	19,728
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(487)	(1,154)	(2,931)	(3,530)
Net change in cash, cash equivalents, and restricted cash	65,112	(44,091)	341,610	147,462
Cash, cash equivalents, and restricted cash at beginning of period	828,676	512,940	552,178	321,387
Cash, cash equivalents, and restricted cash at end of period	893,788	468,849	893,788	468,849
Cash, cash equivalents, and restricted cash at end of period:
Cash, cash equivalents, and restricted cash at end of period	828,676	512,940	552,178	321,387
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	1,739	6,697	5,004	17,268
Excess tax benefits from employee stock plans	8,931	12,006	39,509	31,032
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases	$ 109	$ 314	$ (428)	$ 493