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		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Numerator:
Net loss	$ (38,085)	$ (39,285)	$ (74,722)	$ (79,371)
Denominator:
Weighted-average number of shares outstanding— basic and diluted	140,718	132,981	139,639	132,237
Net loss per share—basic and diluted	$ (0.27)	$ (0.30)	$ (0.54)	$ (0.60)
Class A Common Stock
Numerator:
Net loss	$ (37,001)	$ (27,909)	$ (70,718)	$ (50,163)
Denominator:
Weighted-average number of shares outstanding— basic and diluted	136,712	94,471	132,156	83,574
Net loss per share—basic and diluted	$ (0.27)	$ (0.30)	$ (0.54)	$ (0.60)
Class B Common Stock
Numerator:
Net loss	$ (1,084)	$ (11,376)	$ (4,004)	$ (29,208)
Denominator:
Weighted-average number of shares outstanding— basic and diluted	4,006	38,510	7,483	48,663
Net loss per share—basic and diluted	$ (0.27)	$ (0.30)	$ (0.54)	$ (0.60)