Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Oct. 31, 2019	Apr. 30, 2019	Oct. 31, 2018	Apr. 30, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019	Oct. 31, 2019	Jan. 31, 2019	Oct. 31, 2018
Operating activities:
Net loss	$ (42,717)	$ (18,959)	$ (22,940)	$ (17,041)	$ (90,967)	$ (59,377)	$ (74,837)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					5,836	5,028
Provision for bad debts					297	302
Stock-based compensation expense					50,917	31,943
Deferred income taxes					(58)	(54)
Amortization of deferred financing costs					187	98
Amortization of (discount) premium on marketable securities					(136)	(61)
Amortization of operating lease right-of-use assets					8,039
Changes in operating assets and liabilities:
Accounts receivable					15,908	10,986
Prepaid expenses and other current assets					888	(3,325)
Costs to obtain revenue contracts					(6,196)	(6,860)
Other long term assets					(1,681)	(509)
Accounts payable, accrued expenses and other current liabilities					3,161	4,329
Unearned revenue					(27,531)	(6,985)
Operating lease liabilities					(1,576)
Other long term liabilities					478	(1,095)
Net cash used in operating activities					(42,434)	(25,580)
Investing activities:
Purchases of marketable securities					0	(52,916)
Maturities of marketable securities					51,197	58,420
Capital expenditures					(7,347)	(4,321)
Net cash provided by investing activities					43,850	1,183
Financing activities:
Proceeds from common stock offering, net of underwriting discounts and commissions					147,000	0
Payments of deferred common stock offering issuance costs					(530)	0
Proceeds from exercise of stock options					12,513	15,044
Payments of deferred financing costs					(260)	(159)
Proceeds, net from employee stock purchase plan withholdings					5,078	3,947
Net cash provided by financing activities					163,801	18,832
Effect of exchange rate changes on cash, cash equivalents and restricted cash					(118)	(465)
Net increase in cash, cash equivalents and restricted cash					165,099	(6,030)
Cash, cash equivalents and restricted cash at beginning of period		91,755		34,367	91,755	34,367	34,367
Cash, cash equivalents and restricted cash at end of period	256,854		28,337		256,854	28,337	91,755
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents								$ 244,754	$ 91,755	$ 28,337
Restricted cash								12,100	0	0
Cash, cash equivalents and restricted cash at end of period	$ 256,854	$ 91,755	$ 28,337	$ 34,367	$ 91,755	$ 34,367	$ 91,755	$ 256,854	$ 91,755	$ 28,337