Common Stock - Summary of Shares Available for Grant under Stock Plans (Details) - shares	6 Months Ended	12 Months Ended
	Jul. 31, 2017	Jan. 31, 2017
Equity [Abstract]
Outstanding—January 31, 2016	1,060,592	156,417
Authorized	7,024,194	1,405,316
Options and RSUs granted	(6,957,545)	(1,240,032)
Options and RSUs canceled	3,462,345	738,891
Outstanding—January 31, 2017	4,589,586	1,060,592