Net Loss per Share Attributable to Common Stockholders - 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, 2015	Jul. 31, 2014	Jul. 31, 2015	Jul. 31, 2014
Numerator:
Net loss	$ (50,175)	$ (37,562)	$ (97,458)	$ (76,073)
Add: accretion of redeemable convertible preferred stock	0	(1,791)	0	(1,834)
Net loss attributable to common stockholders	$ (50,175)	$ (39,353)	$ (97,458)	$ (77,907)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	120,399	14,533	119,897	14,140
Net loss per share attributable to common stockholders—basic and diluted	$ (0.42)	$ (2.71)	$ (0.81)	$ (5.51)
Class A Common Stock
Numerator:
Net loss	$ (9,391)	$ 0	$ (15,396)	$ 0
Add: accretion of redeemable convertible preferred stock	0	0	0	0
Net loss attributable to common stockholders	$ (9,391)	$ 0	$ (15,396)	$ 0
Denominator:
Weighted-average number of shares outstanding—basic and diluted	22,535	0	18,941	0
Net loss per share attributable to common stockholders—basic and diluted	$ (0.42)	$ 0	$ (0.81)	$ 0
Class B Common Stock
Numerator:
Net loss	$ (40,784)	$ (37,562)	$ (82,062)	$ (76,073)
Add: accretion of redeemable convertible preferred stock	0	(1,791)	0	(1,834)
Net loss attributable to common stockholders	$ (40,784)	$ (39,353)	$ (82,062)	$ (77,907)
Denominator:
Weighted-average number of shares outstanding—basic and diluted	97,864	14,533	100,956	14,140
Net loss per share attributable to common stockholders—basic and diluted	$ (0.42)	$ (2.71)	$ (0.81)	$ (5.51)