Net Loss per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Numerator:
Net loss	$ (40,196)	$ (42,924)	$ (114,918)	$ (122,295)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	142,366	134,636	140,559	133,044
Net loss per share—basic and diluted	$ (0.28)	$ (0.32)	$ (0.82)	$ (0.92)
Class A Common Stock
Numerator:
Net loss	$ (40,196)	$ (35,061)	$ (110,868)	$ (84,998)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	142,366	109,972	135,605	92,469
Net loss per share—basic and diluted	$ (0.28)	$ (0.32)	$ (0.82)	$ (0.92)
Class B Common Stock
Numerator:
Net loss		$ (7,863)	$ (4,050)	$ (37,297)
Denominator:
Weighted-average number of shares outstanding—basic and diluted		24,664	4,954	40,575
Net loss per share—basic and diluted		$ (0.32)	$ (0.82)	$ (0.92)