Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock Convertible Preferred Stock	Common Stock	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Jan. 31, 2019	$ (6,558)	$ 72	$ 0	$ 30	$ 0	$ 363,076	$ (1,096)	$ (368,640)
Beginning balance (in shares) at Jan. 31, 2019		72,482,609	0	29,755,883	3,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options	16,451		$ 4	$ 1		16,446
Exercise of employee stock options (in shares)			2,617,886	1,370,818
Release of restricted stock units (in shares)			455,328
Stock-based compensation	80,296					80,296
Conversion of common stock			$ 31	$ (31)
Conversion of common stock (in shares)			31,129,701	(31,126,701)	(3,000)
Conversion of preferred stock		$ (77)	$ 77
Conversion of preferred stock (in 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 underwriters' discounts and commissions and concurrent private placement (in shares)			16,680,000
Repurchase of early exercised stock options (in shares)			(823)
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 (in shares)		4,666,666
Vesting of early exercised stock options	453					453
Payments for employee taxes withheld upon vesting of restricted stock units	(15,592)		$ (2)			(15,590)
Warrant exercises (in shares)			121,915
Other comprehensive loss	337						337
Net loss	(80,463)							(80,463)
Ending balance at Oct. 31, 2019	384,344	$ 0	$ 127	$ 0	$ 0	834,079	(759)	(449,103)
Ending balance (in shares) at Oct. 31, 2019		0	128,153,282	0	0
Beginning balance at Jul. 31, 2019	397,531	$ 0	$ 127	$ 0	$ 0	809,014	(2,127)	(409,483)
Beginning balance (in shares) at Jul. 31, 2019		0	126,920,943	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options	3,433		$ 2			3,431
Exercise of employee stock options (in shares)			728,593
Release of restricted stock units (in shares)			455,328
Stock-based compensation	37,155					37,155
Repurchase of early exercised stock options (in shares)			(198)
Vesting of early exercised stock options	69					69
Payments for employee taxes withheld upon vesting of restricted stock units	(15,592)		$ (2)			(15,590)
Warrant exercises (in shares)			48,616
Other comprehensive loss	1,368						1,368
Net loss	(39,620)							(39,620)
Ending balance at Oct. 31, 2019	384,344	$ 0	$ 127	$ 0	$ 0	834,079	(759)	(449,103)
Ending balance (in shares) at Oct. 31, 2019		0	128,153,282	0	0
Beginning balance at Jan. 31, 2020	397,796	$ 0	$ 132	$ 0	$ 0	878,843	(206)	(480,973)
Beginning balance (in shares) at Jan. 31, 2020		0	132,346,402	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options	$ 57,454		$ 12			57,442
Exercise of employee stock options (in shares)	12,710,980		12,710,980
Release of restricted stock units (in shares)			3,882,280
Issuance of shares from share purchase plan	$ 17,828		$ 1			17,827
Issuance of shares from share purchase plan (in shares)			1,040,220
Stock-based compensation	81,453					81,453
Equity component of convertible senior notes, net of issuance costs	118,662					118,662
Purchase of capped calls related to convertible senior notes	(61,870)					(61,870)
Other comprehensive loss	(951)						(951)
Net loss	(99,886)							(99,886)
Ending balance at Oct. 31, 2020	510,486	$ 0	$ 145	$ 0	$ 0	1,092,357	(1,157)	(580,859)
Ending balance (in shares) at Oct. 31, 2020		0	149,979,882	0	0
Beginning balance at Jul. 31, 2020	436,103	$ 0	$ 142	$ 0	$ 0	986,232	(1,571)	(548,700)
Beginning balance (in shares) at Jul. 31, 2020		0	145,554,351	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee stock options	16,760		$ 3			16,757
Exercise of employee stock options (in shares)			2,857,497
Release of restricted stock units (in shares)			1,119,546
Issuance of shares from share purchase plan	7,561					7,561
Issuance of shares from share purchase plan (in shares)			448,488
Stock-based compensation	25,015					25,015
Equity component of convertible senior notes, net of issuance costs	118,662					118,662
Purchase of capped calls related to convertible senior notes	(61,870)					(61,870)
Other comprehensive loss	414						414
Net loss	(32,159)							(32,159)
Ending balance at Oct. 31, 2020	$ 510,486	$ 0	$ 145	$ 0	$ 0	$ 1,092,357	$ (1,157)	$ (580,859)
Ending balance (in shares) at Oct. 31, 2020		0	149,979,882	0	0