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, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Numerator:
Net loss	$ (42,924)	$ (38,233)	$ (122,295)	$ (114,910)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	134,636	128,275	133,044	126,712
Net loss per share—basic and diluted	$ (0.32)	$ (0.30)	$ (0.92)	$ (0.91)
Class A Common Stock
Numerator:
Net loss	$ (35,061)	$ (16,978)	$ (84,998)	$ (46,036)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	109,972	56,964	92,469	50,764
Net loss per share—basic and diluted	$ (0.32)	$ (0.30)	$ (0.92)	$ (0.91)
Class B Common Stock
Numerator:
Net loss	$ (7,863)	$ (21,255)	$ (37,297)	$ (68,874)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	24,664	71,311	40,575	75,948
Net loss per share—basic and diluted	$ (0.32)	$ (0.30)	$ (0.92)	$ (0.91)