Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (166,354)	$ (124,427)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	43,591	33,590
Amortization of debt discount and debt issuance costs	13,290	7,889
Stock-based compensation expense	120,561	97,609
Other	327	82
Changes in operating assets and liabilities, net of effects of acquisition:
Accounts receivable, net	26,553	707
Inventory	6,852	(8,900)
Deferred commissions	(3,595)	(4,155)
Prepaid expenses and other assets	(635)	11,134
Operating lease right-of-use assets	13,438	0
Accounts payable	(30,827)	(18,135)
Accrued compensation and other liabilities	(25,704)	(7,458)
Operating lease liabilities	(13,083)	0
Deferred revenue	71,045	39,144
Net cash provided by operating activities	55,459	27,080
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(53,229)	(42,733)
Acquisition, net of cash acquired	(47,881)	0
Purchase of intangible assets	(9,000)	0
Purchases of marketable securities	(488,497)	(494,507)
Sales of marketable securities	60,368	13,585
Maturities of marketable securities	270,756	97,793
Net cash used in investing activities	(267,483)	(425,862)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from exercise of stock options	19,260	29,067
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	(7,173)	0
Repurchase of common stock	0	(20,000)
Net cash provided by financing activities	32,574	526,197
Net increase (decrease) in cash, cash equivalents and restricted cash	(179,450)	127,415
Cash, cash equivalents and restricted cash, beginning of period	463,813	258,820
Cash, cash equivalents and restricted cash, end of period	284,363	386,235
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	2,716	3,023
Cash paid for interest	359	0
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION
Property and equipment purchased but not yet paid	5,717	11,949
Vesting of early exercised stock options	$ 0	$ 320