CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Class A and Class B Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Accumulated Deficit
Beginning balance (in shares) at Jan. 31, 2019		54,321,810
Beginning balance at Jan. 31, 2019	$ 264,566	$ 54	$ 754,612	$ (1,319)	$ (174)	$ (488,607)	$ (4,103)	$ (4,103)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		831,901
Stock option exercises	6,438	$ 1	6,437
Repurchase of early exercised options (in shares)		(3,981)
Vesting of early exercised stock options	127		127
Vesting of restricted stock units (in shares)		126,346
Stock-based compensation	14,009		14,009
Unrealized gain (loss) on available-for-sale securities	58				58
Foreign currency translation adjustment	13				13
Net loss	(33,240)					(33,240)
Ending balance (in shares) at Apr. 30, 2019		55,276,076
Ending balance at Apr. 30, 2019	247,868	$ 55	775,185	(1,319)	(103)	(525,950)
Beginning balance (in shares) at Jan. 31, 2019		54,321,810
Beginning balance at Jan. 31, 2019	264,566	$ 54	754,612	(1,319)	(174)	(488,607)	(4,103)	(4,103)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized gain (loss) on available-for-sale securities	79
Foreign currency translation adjustment	(237)
Net loss	(70,576)
Ending balance (in shares) at Jul. 31, 2019		56,238,616
Ending balance at Jul. 31, 2019	239,343	$ 56	804,224	(1,319)	(332)	(563,286)
Beginning balance (in shares) at Apr. 30, 2019		55,276,076
Beginning balance at Apr. 30, 2019	247,868	$ 55	775,185	(1,319)	(103)	(525,950)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		665,543
Stock option exercises	4,914	$ 1	4,913
Repurchase of early exercised options (in shares)		(209)
Vesting of early exercised stock options	70		70
Vesting of restricted stock units (in shares)		206,587
Stock-based compensation	17,662		17,662
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		90,619
Issuance of common stock under the Employee Stock Purchase Plan	6,394		6,394
Unrealized gain (loss) on available-for-sale securities	21				21
Foreign currency translation adjustment	(250)				(250)
Net loss	(37,336)					(37,336)
Ending balance (in shares) at Jul. 31, 2019		56,238,616
Ending balance at Jul. 31, 2019	239,343	$ 56	804,224	(1,319)	(332)	(563,286)
Beginning balance (in shares) at Jan. 31, 2020		57,382,543
Beginning balance at Jan. 31, 2020	82,858	$ 57	752,127	(1,319)	225	(668,232)	(227)	(227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		373,394
Stock option exercises	2,995	$ 1	2,994
Repurchase of early exercised options (in shares)		(79)
Vesting of early exercised stock options	42		42
Vesting of restricted stock units (in shares)		241,569
Stock-based compensation	30,567		30,567
Conversion of 2024 convertible senior notes (in shares)		8
Unrealized gain (loss) on available-for-sale securities	848				848
Foreign currency translation adjustment	(75)				(75)
Net loss	(53,967)					(53,967)
Ending balance (in shares) at Apr. 30, 2020		57,997,435
Ending balance at Apr. 30, 2020	63,041	$ 58	785,730	(1,319)	998	(722,426)
Beginning balance (in shares) at Jan. 31, 2020		57,382,543
Beginning balance at Jan. 31, 2020	$ 82,858	$ 57	752,127	(1,319)	225	(668,232)	$ (227)	$ (227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)	844,663
Unrealized gain (loss) on available-for-sale securities	$ 317
Foreign currency translation adjustment	(473)
Net loss	(118,492)
Ending balance (in shares) at Jul. 31, 2020		58,857,733
Ending balance at Jul. 31, 2020	48,151	$ 59	836,293	(1,319)	69	(786,951)
Beginning balance (in shares) at Apr. 30, 2020		57,997,435
Beginning balance at Apr. 30, 2020	63,041	$ 58	785,730	(1,319)	998	(722,426)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		471,269
Stock option exercises	4,051	$ 1	4,050
Repurchase of early exercised options (in shares)		(881)
Vesting of early exercised stock options	25		25
Vesting of restricted stock units (in shares)		305,428
Stock-based compensation	37,525		37,525
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		84,482
Issuance of common stock under the Employee Stock Purchase Plan	8,963		8,963
Unrealized gain (loss) on available-for-sale securities	(531)				(531)
Foreign currency translation adjustment	(398)				(398)
Net loss	(64,525)					(64,525)
Ending balance (in shares) at Jul. 31, 2020		58,857,733
Ending balance at Jul. 31, 2020	$ 48,151	$ 59	$ 836,293	$ (1,319)	$ 69	$ (786,951)