Net Loss per Share Attributable to Common Stockholders - Summary of Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	[1]	Oct. 31, 2018	Oct. 31, 2017	[1]
Earnings Per Share [Abstract]
Net loss	$ (28,180)	$ (29,404)	[2]	$ (152,607)	$ (144,974)	[2],[3]
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	235,205	213,274		229,505	209,456
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.12)	$ (0.14)		$ (0.66)	$ (0.69)

[1] * Prior period information has been adjusted to reflect the adoption impact of ASC 606, which we adopted on February 1, 2018.

[2] * Prior period information has been adjusted to reflect the adoption impact of ASC 606, which we adopted on February 1, 2018.

[3] * Prior period information has been adjusted to reflect the adoption impact of ASC 606 and Accounting Standards Update No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18), which we adopted on February 1, 2018