Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (100,336)	$ (64,304)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	21,060	16,417
Amortization of debt discount and debt issuance costs	6,490	1,455
Stock-based compensation expense	62,157	43,955
Other	(811)	152
Changes in operating assets and liabilities, net of effects of acquisition:
Accounts receivable, net	67,299	47,143
Inventory	(2,023)	(4,429)
Deferred commissions	1,716	1,269
Prepaid expenses and other assets	(7,298)	11,111
Operating lease right-of-use assets	6,209	0
Accounts payable	(25,807)	(18,802)
Accrued compensation and other liabilities	(43,993)	(29,881)
Operating lease liabilities	(6,034)	0
Deferred revenue	28,013	14,510
Net cash provided by operating activities	6,642	18,596
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(24,296)	(22,296)
Acquisition, net of cash acquired	(47,881)	0
Purchases of marketable securities	(312,859)	(81,702)
Sales of marketable securities	22,344	10,454
Maturities of marketable securities	164,139	61,023
Net cash used in investing activities	(198,553)	(32,521)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options	16,761	9,614
Proceeds from issuance of common stock under employee stock purchase plan	32,042	19,698
Proceeds from issuance of convertible senior notes, net of issuance costs	0	562,062
Payment for purchase of capped calls	0	(64,630)
Repayment of debt assumed from acquisition	(11,555)	0
Tax withholding on vesting of restricted stock	(5,672)	0
Repurchase of common stock	0	(20,000)
Net cash provided by financing activities	31,576	506,744
Net increase (decrease) in cash, cash equivalents and restricted cash	(160,335)	492,819
Cash, cash equivalents and restricted cash, beginning of period	463,813	258,820
Cash, cash equivalents and restricted cash, end of period	303,478	751,639
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD:
Cash, cash equivalents and restricted cash, end of period	463,813	258,820
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	1,640	1,839
Cash paid for interest	359	0
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid	11,595	8,316
Vesting of early exercised stock options	$ 0	$ 320