CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Other Comprehensive Income (Loss)	Accumulated Deficit	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Additional Paid-In Capital	Cumulative Effect, Period of Adoption, Adjustment Accumulated Deficit
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 restricted stock units (in shares)		241,569
Vesting of early exercised stock options	42		42
Stock-based compensation	30,567		30,567
Conversion of 2024 convertible senior notes (in shares)		8
Unrealized gain 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]
Unrealized gain on available-for-sale securities	(24)
Foreign currency translation adjustment	(538)
Net loss	(191,143)
Ending balance (in shares) at Oct. 31, 2020		60,156,153
Ending balance at Oct. 31, 2020	21,804	$ 60	883,002	(1,319)	(337)	(859,602)
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 restricted stock units (in shares)		305,428
Vesting of early exercised stock options	25		25
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 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		987,837
Stock option exercises	6,739	$ 1	6,738
Vesting of restricted stock units (in shares)		310,573
Vesting of early exercised stock options	19		19
Stock-based compensation	39,952		39,952
Conversion of 2024 convertible senior notes (in shares)		10
Unrealized gain on available-for-sale securities	(341)				(341)
Foreign currency translation adjustment	(65)				(65)
Net loss	(72,651)					(72,651)
Ending balance (in shares) at Oct. 31, 2020		60,156,153
Ending balance at Oct. 31, 2020	$ 21,804	$ 60	883,002	(1,319)	(337)	(859,602)
Beginning balance (in shares) at Jan. 31, 2021	60,898,451	60,898,451
Beginning balance at Jan. 31, 2021	$ (5,033)	$ 61	932,332	(1,319)	(704)	(935,403)	(256,746)	$ (309,381)	52,635
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		483,787
Stock option exercises	3,540	$ 1	3,539
Vesting of restricted stock units (in shares)		341,939
Vesting of early exercised stock options	10		10
Stock-based compensation	50,914		50,914
Conversion of 2024 convertible senior notes (in shares)		372,096
Conversion of convertible senior notes	2,999		2,999
Unrealized gain on available-for-sale securities	34				34
Foreign currency translation adjustment	(90)				(90)
Net loss	(63,992)					(63,992)
Ending balance (in shares) at Apr. 30, 2021		62,096,273
Ending balance at Apr. 30, 2021	$ (268,364)	$ 62	680,413	(1,319)	(760)	(946,760)
Beginning balance (in shares) at Jan. 31, 2021	60,898,451	60,898,451
Beginning balance at Jan. 31, 2021	$ (5,033)	$ 61	932,332	(1,319)	(704)	(935,403)	$ (256,746)	(309,381)	52,635
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)	986,002
Unrealized gain on available-for-sale securities	$ (350)
Foreign currency translation adjustment	(238)
Net loss	(222,418)
Ending balance (in shares) at Oct. 31, 2021		66,716,713
Ending balance at Oct. 31, 2021	662,905	$ 67	1,770,635	(1,319)	(1,292)	(1,105,186)		309,400	52,600
Beginning balance (in shares) at Apr. 30, 2021		62,096,273
Beginning balance at Apr. 30, 2021	(268,364)	$ 62	680,413	(1,319)	(760)	(946,760)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		282,519
Stock option exercises	2,206	$ 0	2,206
Vesting of restricted stock units (in shares)		362,342
Stock-based compensation	57,705		57,705
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		45,261
Issuance of common stock under the Employee Stock Purchase Plan	12,963		12,963
Conversion of 2024 convertible senior notes (in shares)		844,194
Conversion of convertible senior notes	56,683	$ 1	56,682
Issuance of common stock, net of issuance costs (in shares)		2,500,000
Issuance of common stock, net of issuance costs	889,184	$ 3	889,181
Unrealized gain on available-for-sale securities	(86)				(86)
Foreign currency translation adjustment	566				566
Net loss	(77,133)					(77,133)
Ending balance (in shares) at Jul. 31, 2021		66,130,589
Ending balance at Jul. 31, 2021	673,724	$ 66	1,699,150	(1,319)	(280)	(1,023,893)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises (in shares)		219,696
Stock option exercises	1,848	$ 0	1,848
Vesting of restricted stock units (in shares)		366,226
Vesting of restricted stock units	1	$ 1
Stock-based compensation	69,620		69,620
Conversion of 2024 convertible senior notes (in shares)		202
Conversion of convertible senior notes	17		17
Unrealized gain on available-for-sale securities	(298)				(298)
Foreign currency translation adjustment	(714)				(714)
Net loss	(81,293)					(81,293)
Ending balance (in shares) at Oct. 31, 2021		66,716,713
Ending balance at Oct. 31, 2021	$ 662,905	$ 67	$ 1,770,635	$ (1,319)	$ (1,292)	$ (1,105,186)		$ 309,400	$ 52,600