CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Cash flows from operating activities
Net loss	$ (66,779,000)	$ (38,953,000)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	19,165,000	6,720,000
Accretion of discounts on marketable securities, net	374,000	(956,000)
Amortization of deferred commissions	6,675,000	4,127,000
Amortization of debt discount and issuance costs	23,350,000	8,595,000
Stock-based compensation	60,068,000	38,690,000
Other	(637,000)	(374,000)
Changes in operating assets and liabilities net of effects from acquisitions:
Accounts receivable	23,855,000	12,391,000
Prepaid expenses and other current assets	(9,839,000)	(3,304,000)
Other assets	(2,998,000)	(542,000)
Deferred commissions	(15,491,000)	(8,467,000)
Accounts payable	(4,126,000)	2,458,000
Accrued expenses and other liabilities	6,895,000	6,362,000
Deferred revenue	5,365,000	1,216,000
Net cash provided by operating activities	45,877,000	27,963,000
Cash flows from investing activities
Purchases of marketable securities	(318,759,000)	(209,331,000)
Maturities of marketable securities	44,796,000	31,834,000
Sales of marketable securities	199,314,000
Acquisitions, net of cash acquired	(208,505,000)	(49,211,000)
Purchases of property and equipment	(9,862,000)	(4,870,000)
Net cash used in investing activities	(293,016,000)	(231,578,000)
Cash flows from financing activities
Proceeds from issuance of convertible senior notes, net of issuance costs	786,157,000	(639,000)
Purchase of capped calls	(118,738,000)
Proceeds from the exercise of common stock options	14,095,000	10,174,000
Proceeds from issuance of common stock for employee stock purchase plan	11,455,000	8,778,000
Net cash provided by financing activities	692,969,000	18,313,000
Net increase (decrease) in cash, cash equivalents, and restricted cash	445,830,000	(185,302,000)
Cash, cash equivalents, and restricted cash at beginning of year	141,319,000	412,976,000
Cash, cash equivalents, and restricted cash at end of period	587,149,000	227,674,000
Reconciliation of cash, cash equivalents, and restricted cash to the condensed consolidated balance sheets
Cash and cash equivalents	587,029,000	227,606,000
Restricted cash included in other assets	$ 120,000	$ 68,000
Restricted cash, asset, statement of financial position [Extensible List]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Total cash, cash equivalents, and restricted cash	$ 587,149,000	$ 227,674,000
Supplemental disclosure of cash flow data
Cash paid for income taxes	1,584,000	4,056,000
Cash paid for interest	543,000	426,000
Supplemental disclosure of non-cash investing and financing activities
Vesting of early exercised stock options		273,000
Property and equipment included in accounts payable and accrued expenses and other liabilities	$ 537,000	$ 897,000