Common Stock and Stockholders' Equity (Deficit) - Schedule of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)	0	59,494,582
Redeemable convertible preferred stock, shares issued (in shares)	0	59,465,439
Redeemable convertible preferred stock, shares outstanding (in shares)	0	59,465,439	59,465,439	53,223,503
Redeemable convertible preferred stock, liquidation preference	$ 0	$ 230,373
Redeemable convertible preferred stock, carrying value	$ 0	$ 227,954	$ 227,954	$ 154,530
Series A
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		14,210,789
Redeemable convertible preferred stock, shares issued (in shares)		14,210,783
Redeemable convertible preferred stock, shares outstanding (in shares)		14,210,783
Redeemable convertible preferred stock, liquidation preference		$ 11,373
Redeemable convertible preferred stock, carrying value		$ 11,322
Series B
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		12,015,123
Redeemable convertible preferred stock, shares issued (in shares)		11,986,055
Redeemable convertible preferred stock, shares outstanding (in shares)		11,986,055
Redeemable convertible preferred stock, liquidation preference		$ 16,500
Redeemable convertible preferred stock, carrying value		$ 16,420
Series C
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		10,708,782
Redeemable convertible preferred stock, shares issued (in shares)		10,708,780
Redeemable convertible preferred stock, shares outstanding (in shares)		10,708,780
Redeemable convertible preferred stock, liquidation preference		$ 25,000
Redeemable convertible preferred stock, carrying value		$ 24,872
Series D
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		6,833,654
Redeemable convertible preferred stock, shares issued (in shares)		6,833,651
Redeemable convertible preferred stock, shares outstanding (in shares)		6,833,651
Redeemable convertible preferred stock, liquidation preference		$ 27,500
Redeemable convertible preferred stock, carrying value		$ 27,416
Series E
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		9,484,234
Redeemable convertible preferred stock, shares issued (in shares)		9,484,234
Redeemable convertible preferred stock, shares outstanding (in shares)		9,484,234
Redeemable convertible preferred stock, liquidation preference		$ 75,000
Redeemable convertible preferred stock, carrying value		$ 74,500
Series F
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares authorized (in shares)		6,242,000
Redeemable convertible preferred stock, shares issued (in shares)		6,241,936
Redeemable convertible preferred stock, shares outstanding (in shares)		6,241,936
Redeemable convertible preferred stock, liquidation preference		$ 75,000
Redeemable convertible preferred stock, carrying value		$ 73,424