CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Class A Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance, Beginning at Jan. 31, 2019	$ 31,405	$ 14	$ 1,166,443	$ (1,177)	$ 23	$ (1,133,898)
Balance, Beginning, Shares at Jan. 31, 2019		144,311,000
Issuance of common stock upon stock option exercises	1,213		1,213
Issuance of common stock upon stock option exercises (in shares)		152,000
Stock-based compensation related to stock awards	35,678		35,678
Vesting of restricted stock units, net of shares withheld for employee payroll taxes	1	$ 1
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		1,205,000
Employee payroll taxes withheld related to vesting of restricted stock units	(14,624)		(14,624)
Common stock issued under employee stock purchase plan	13,605		13,605
Common stock issued under employee stock purchase plan (in shares)		829,000
Other comprehensive income (loss)	88				88
Net loss	(36,828)					(36,828)
Balance, Ending at Apr. 30, 2019	30,538	$ 15	1,202,315	(1,177)	111	(1,170,726)
Balance, Ending, Shares at Apr. 30, 2019		146,497,000
Balance, Beginning at Jan. 31, 2019	31,405	$ 14	1,166,443	(1,177)	23	(1,133,898)
Balance, Beginning, Shares at Jan. 31, 2019		144,311,000
Other comprehensive income (loss)	(134)
Net loss	(113,958)
Balance, Ending at Oct. 31, 2019	20,775	$ 15	1,269,904	(1,177)	(111)	(1,247,856)
Balance, Ending, Shares at Oct. 31, 2019		149,478,000
Balance, Beginning at Apr. 30, 2019	30,538	$ 15	1,202,315	(1,177)	111	(1,170,726)
Balance, Beginning, Shares at Apr. 30, 2019		146,497,000
Issuance of common stock upon stock option exercises	1,031		1,031
Issuance of common stock upon stock option exercises (in shares)		143,000
Stock-based compensation related to stock awards	38,035		38,035
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		1,082,000
Employee payroll taxes withheld related to vesting of restricted stock units	(10,940)		(10,940)
Other comprehensive income (loss)	(164)				(164)
Net loss	(36,234)					(36,234)
Balance, Ending at Jul. 31, 2019	22,266	$ 15	1,230,441	(1,177)	(53)	(1,206,960)
Balance, Ending, Shares at Jul. 31, 2019		147,722,000
Issuance of common stock upon stock option exercises	764		764
Issuance of common stock upon stock option exercises (in shares)		122,000
Stock-based compensation related to stock awards	38,373		38,373
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		989,000
Employee payroll taxes withheld related to vesting of restricted stock units	(9,494)		(9,494)
Common stock issued under employee stock purchase plan	9,820		9,820
Common stock issued under employee stock purchase plan (in shares)		645,000
Other comprehensive income (loss)	(58)				(58)
Net loss	(40,896)					(40,896)
Balance, Ending at Oct. 31, 2019	20,775	$ 15	1,269,904	(1,177)	(111)	(1,247,856)
Balance, Ending, Shares at Oct. 31, 2019		149,478,000
Balance, Beginning at Jan. 31, 2020	22,357	$ 15	1,302,072	(1,177)	(307)	(1,278,246)
Balance, Beginning, Shares at Jan. 31, 2020		150,611,000
Issuance of common stock upon stock option exercises	965		965
Issuance of common stock upon stock option exercises (in shares)		222,000
Stock-based compensation related to stock awards	42,766		42,766
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		1,331,000
Employee payroll taxes withheld related to vesting of restricted stock units	(10,264)		(10,264)
Common stock issued under employee stock purchase plan	11,906		11,906
Common stock issued under employee stock purchase plan (in shares)		1,282,000
Other comprehensive income (loss)	(1,332)				(1,332)
Net loss	(25,550)					(25,550)
Balance, Ending at Apr. 30, 2020	40,848	$ 15	1,347,445	(1,177)	(1,639)	(1,303,796)
Balance, Ending, Shares at Apr. 30, 2020		153,446,000
Balance, Beginning at Jan. 31, 2020	$ 22,357	$ 15	1,302,072	(1,177)	(307)	(1,278,246)
Balance, Beginning, Shares at Jan. 31, 2020		150,611,000
Issuance of common stock upon stock option exercises (in shares)	1,830,313
Other comprehensive income (loss)	$ (990)
Net loss	(38,490)
Balance, Ending at Oct. 31, 2020	87,562	$ 16	1,406,756	(1,177)	(1,297)	(1,316,736)
Balance, Ending, Shares at Oct. 31, 2020		158,643,000
Balance, Beginning at Apr. 30, 2020	40,848	$ 15	1,347,445	(1,177)	(1,639)	(1,303,796)
Balance, Beginning, Shares at Apr. 30, 2020		153,446,000
Issuance of common stock upon stock option exercises	7,548		7,548
Issuance of common stock upon stock option exercises (in shares)		1,377,000
Stock-based compensation related to stock awards	35,767		35,767
Vesting of restricted stock units, net of shares withheld for employee payroll taxes	1	$ 1
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		1,576,000
Employee payroll taxes withheld related to vesting of restricted stock units	(17,180)		(17,180)
Other comprehensive income (loss)	264				264
Net loss	(7,656)					(7,656)
Balance, Ending at Jul. 31, 2020	59,592	$ 16	1,373,580	(1,177)	(1,375)	(1,311,452)
Balance, Ending, Shares at Jul. 31, 2020		156,399,000
Issuance of common stock upon stock option exercises	1,361		1,361
Issuance of common stock upon stock option exercises (in shares)		231,000
Stock-based compensation related to stock awards	35,902		35,902
Vesting of restricted stock units, net of shares withheld for employee payroll taxes (in shares)		1,150,000
Employee payroll taxes withheld related to vesting of restricted stock units	(10,776)		(10,776)
Common stock issued under employee stock purchase plan	6,689		6,689
Common stock issued under employee stock purchase plan (in shares)		863,000
Other comprehensive income (loss)	78				78
Net loss	(5,284)					(5,284)
Balance, Ending at Oct. 31, 2020	$ 87,562	$ 16	$ 1,406,756	$ (1,177)	$ (1,297)	$ (1,316,736)
Balance, Ending, Shares at Oct. 31, 2020		158,643,000