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 loss	$ (208,359)	$ (426,458)	$ (52,276)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	50,182	38,027	31,750
Amortization of deferred contract acquisition and fulfillment costs	69,747	42,112	30,377
Amortization of debt discount and transaction costs	26,389	9,507	0
Non-cash operating lease costs	19,435	0	0
Stock-based compensation expense	206,404	410,978	29,747
Deferred income taxes	1,287	(5,001)	(996)
Other	(1,741)	800	(1,877)
Changes in operating assets and liabilities
Accounts receivable	(63,293)	(42,571)	(28,077)
Contract assets	(1,508)	4,204	(6,934)
Prepaid expenses and other current assets	(3,142)	(3,283)	(1,507)
Deferred contract acquisition and fulfillment costs	(115,723)	(80,869)	(52,978)
Other assets	1,538	2,658	(1,604)
Accounts payable	3,849	(7,380)	2,864
Accrued expenses and other liabilities	9,353	6,449	9,548
Accrued compensation	5,636	26,039	9,168
Contract liabilities	130,266	100,874	87,774
Operating lease liabilities	(14,624)	0	0
Net cash provided by operating activities	115,696	76,086	54,979
Cash flows from investing activities:
Purchases of marketable securities	(861,252)	(415,132)	0
Maturities of marketable securities	627,309	0	0
Purchases of strategic investments	(15,500)	0	0
Cash paid for acquisition, net of acquired cash	0	(218,779)	(299)
Purchases of property and equipment	(72,046)	(30,413)	(18,929)
Proceeds from sale of business held for sale	0	0	467
Net cash used in investing activities	(321,489)	(664,324)	(18,761)
Cash flows from financing activities:
Proceeds from issuance of convertible senior notes, net of initial purchasers' discounts and transaction costs	0	560,756	0
Purchase of capped calls related to issuance of convertible senior notes	0	(67,563)	0
Proceeds from issuance of common stock in initial public offering, net of underwriting commissions	0	529,305	0
Payment of tax withholding obligation on RSU settlement	(166,504)	(215,332)	0
Proceeds from exercise of stock options	72,177	50,211	26,433
Proceeds from employee stock purchase plan	23,872	0	0
Payment of deferred offering costs	0	(4,011)	(315)
Other financing	0	(250)	(390)
Net cash provided by (used in) financing activities	(70,455)	853,116	25,728
Effect of foreign exchange on cash, cash equivalents and restricted cash	(447)	(4,136)	4,246
Net increase (decrease) in cash, cash equivalents and restricted cash	(276,695)	260,742	66,192
Cash, cash equivalents and restricted cash at beginning of period	518,178	257,436	191,244
Cash, cash equivalents and restricted cash at end of period	241,483	518,178	257,436
Supplemental disclosure:
Cash paid for interest	2,852	204	599
Cash paid for operating lease liabilities	22,034	0	0
Cash paid for taxes	1,970	3,213	617
Non-cash investing and financing activities:
Property and equipment in accounts payable and accrued expenses and other current liabilities	14,082	2,293	3,967
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering	0	547,854	0
Conversion of preferred stock warrant to common stock warrant in connection with initial public offering	0	848	0
Preferred stock accretion	0	353	1,461
Recognition of build-to-suit lease	0	2,479	0
Operating lease right-of-use assets exchanged for lease obligations	77,391	0	0
Derecognition of build-to-suit lease	2,479	0	0
Deferred offering costs accrued and unpaid	$ 0	$ 0	$ 1,381