Common Stock - Summary of Shares Available for Grant under Stock Plans (Details) - shares	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Equity [Abstract]
Available for grant, beginning balance	1,060,592	156,417
Authorized	7,024,194	1,405,316
Options and RSUs granted	(8,738,088)	(1,240,032)
Options and RSUs canceled	1,661,703	738,891
Available for grant, ending balance	1,008,401	1,060,592