Condensed Consolidated Statements of Stockholders' Equity(Deficit) (Unaudited) - USD ($) $ in Thousands	Total	IPO	Convertible Preferred Stock	Common Stock, Class A	Common Stock, Class B	Common Stock	Common Stock IPO	Additional Paid-In Capital	Additional Paid-In Capital IPO	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Jan. 31, 2018	$ 35,057		$ 72	$ 24				$ 322,300		$ (1,120)	$ (286,219)
Beginning Balance, shares at Jan. 31, 2018			72,394,601	24,637,801	3,000
Cumulative effect of the adoption of ASU 2016-09 | Accounting Standards Update 2016-09								187			(187)
Exercise of employee stock options	4,133			$ 2				4,131
Exercise of employee stock options, shares				2,004,837
Vesting of early exercised stock options	444							444
Repurchase of early exercised stock options, shares				(19,440)
Issuance of shares at end of escrow period in connection with prior period acquisitions, shares				81,433
Stock-based compensation	13,121							13,121
Other comprehensive loss	(1,119)									(1,119)
Net loss	(55,675)										(55,675)
Ending Balance at Jul. 31, 2018	(4,039)		$ 72	$ 26				340,183		(2,239)	(342,081)
Ending Balance, shares at Jul. 31, 2018			72,394,601	26,704,631	3,000
Beginning Balance at Apr. 30, 2018	16,083		$ 72	$ 25				331,224		(1,304)	(313,934)
Beginning Balance, shares at Apr. 30, 2018			72,394,601	25,978,565	3,000
Exercise of employee stock options	2,260			$ 1				2,259
Exercise of employee stock options, shares				733,067
Vesting of early exercised stock options	216							216
Repurchase of early exercised stock options, shares				(7,001)
Stock-based compensation	6,484							6,484
Other comprehensive loss	(935)									(935)
Net loss	(28,147)										(28,147)
Ending Balance at Jul. 31, 2018	(4,039)		$ 72	$ 26				340,183		(2,239)	(342,081)
Ending Balance, shares at Jul. 31, 2018			72,394,601	26,704,631	3,000
Beginning Balance at Jan. 31, 2019	(6,558)		$ 72	$ 30				363,076		(1,096)	(368,640)
Beginning Balance, shares at Jan. 31, 2019			72,482,609	29,755,883	3,000
Issuance of Series F preferred shares, net of issuance costs	69,848		$ 5					69,843
Issuance of Series F preferred shares, net of issuance costs, shares			4,666,666
Conversion of common stock				$ (31)		$ 31
Conversion of common stock, shares				(31,126,701)	(3,000)	31,129,701
Conversion of preferred stock			$ (77)			$ 77
Conversion of preferred stock, shares			(77,149,275)			77,149,275
Proceeds from Initial Public Offering, net of issuance and underwriter's discounts and commissions and concurrent private placement		$ 319,572					$ 17		$ 319,555
Proceeds from Initial Public Offering, net of issuance and underwriter's discounts and commissions and concurrent private placement, shares							16,680,000
Exercise of employee stock options	$ 13,010			$ 1		$ 2		13,007
Exercise of employee stock options, shares	3,259,840			1,370,818		1,889,293
Vesting of early exercised stock options	$ 392							392
Repurchase of early exercised stock options, shares						(625)
Warrant exercise, shares						73,299
Stock-based compensation	43,141							43,141
Other comprehensive loss	(1,031)									(1,031)
Net loss	(40,843)										(40,843)
Ending Balance at Jul. 31, 2019	397,531					$ 127		809,014		(2,127)	(409,483)
Ending Balance, shares at Jul. 31, 2019						126,920,943
Beginning Balance at Apr. 30, 2019	73,767		$ 77	$ 31				446,355		(1,497)	(371,199)
Beginning Balance, shares at Apr. 30, 2019			77,149,275	31,126,701	3,000
Conversion of common stock				$ (31)		$ 31
Conversion of common stock, shares				(31,126,701)	(3,000)	31,129,701
Conversion of preferred stock			$ (77)			$ 77
Conversion of preferred stock, shares			(77,149,275)			77,149,275
Proceeds from Initial Public Offering, net of issuance and underwriter's discounts and commissions and concurrent private placement		$ 319,572					$ 17		$ 319,555
Proceeds from Initial Public Offering, net of issuance and underwriter's discounts and commissions and concurrent private placement, shares							16,680,000
Exercise of employee stock options	7,742					$ 2		7,740
Exercise of employee stock options, shares						1,889,293
Vesting of early exercised stock options	185							185
Repurchase of early exercised stock options, shares						(625)
Warrant exercise, shares						73,299
Stock-based compensation	35,179							35,179
Other comprehensive loss	(630)									(630)
Net loss	(38,284)										(38,284)
Ending Balance at Jul. 31, 2019	$ 397,531					$ 127		$ 809,014		$ (2,127)	$ (409,483)
Ending Balance, shares at Jul. 31, 2019						126,920,943