Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Cash flows from operating activities
Net income	$ 86,570	$ 73,449
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,878	3,900
Reduction of operating lease right-of-use assets	2,997	1,538
Accretion of discount on short-term investments	(11)	(1,178)
Stock-based compensation	36,907	20,756
Amortization of deferred costs	4,751	4,849
Deferred income taxes	(1,134)	418
(Gain) Loss on foreign currency from mark-to-market derivative	93	(80)
Bad debt recovery	(393)	(153)
Changes in operating assets and liabilities:
Accounts receivable	154,160	139,510
Unbilled accounts receivable	(4,452)	(5,244)
Deferred costs	(3,342)	(4,601)
Income taxes payable	(1,850)	338
Prepaid expenses and other current and long-term assets	551	(2,759)
Accounts payable	(4,430)	(416)
Accrued expenses and other current liabilities	2,691	(759)
Deferred revenue	1,477	7,914
Operating lease liabilities	(2,811)	(1,629)
Other long-term liabilities	2,520	436
Net cash provided by operating activities	282,172	236,289
Cash flows from investing activities
Purchases of short-term investments	(188,818)	(228,894)
Maturities and sales of short-term investments	140,342	188,965
Property and equipment	267	(1,194)
Capitalized internal-use software development costs	0	(419)
Net cash used in investing activities	(48,209)	(41,542)
Cash flows from financing activities
Reduction of lease liabilities - finance leases	(248)	(249)
Proceeds from exercise of common stock options	9,781	3,391
Net cash provided by financing activities	9,533	3,142
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	548	(702)
Net change in cash, cash equivalents, and restricted cash	244,044	197,187
Cash, cash equivalents, and restricted cash at beginning of period	479,797	552,178
Cash, cash equivalents, and restricted cash at end of period	723,841	749,365
Cash, cash equivalents, and restricted cash at end of period:
Cash, cash equivalents, and restricted cash at end of period	723,841	749,365
Supplemental disclosures of other cash flow information:
Cash paid for income taxes, net of refunds	5,866	2,383
Excess tax benefits from employee stock plans	19,615	13,552
Non-cash investing and financing activities:
Changes in accounts payable and accrued expenses related to property and equipment purchases	$ 590	$ (634)