Net Loss Per Share - Schedule 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	$ (39,207)	$ (26,032)	[1],[2]	$ (65,169)	$ (53,738)	[1],[3]
Denominator:
Weighted-average shares outstanding - basic and diluted (in shares)	106,702	93,576	[1]	105,475	67,125	[1]
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.37)	$ (0.28)	[1]	$ (0.62)	$ (0.80)	[1]
Class A Common Stock
Numerator:
Net loss	$ (33,862)	$ (4,075)		$ (53,242)	$ (7,254)
Denominator:
Weighted-average shares outstanding - basic and diluted (in shares)	92,156	14,650		86,172	9,061
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.37)	$ (0.28)		$ (0.62)	$ (0.80)
Class B Common Stock
Numerator:
Net loss	$ (5,345)	$ (21,957)		$ (11,927)	$ (46,484)
Denominator:
Weighted-average shares outstanding - basic and diluted (in shares)	14,546	78,926		19,303	58,064
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.37)	$ (0.28)		$ (0.62)	$ (0.80)

[1] See Note 2 for a summary of adjustments.

[2] See Note 2 for a summary of adjustments.

[3] See Note 2 for a summary of adjustments.