Common Stock - Summary of Stock Option Activity under Stock Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of shares underlying outstanding options, beginning balance	4,467,961
Number of shares underlying outstanding, Options granted	1,580,416
Number of shares underlying outstanding, Options exercised	(219,896)
Number of shares underlying outstanding, Options canceled	(1,475,636)
Number of shares underlying outstanding options, ending balance	4,352,845	4,467,961
Number of shares underlying, Options vested and exercisable	2,908,420
Number of shares underlying, Options vested and expected to vest	4,352,845
Weighted average exercise price, Outstanding beginning balance	$ 18.83
Weighted average exercise price, Options granted	16.72
Weighted average exercise price, Options exercised	10.04
Weighted average exercise price, Options canceled	12.88
Weighted average exercise price, Outstanding ending balance	12.49	$ 18.83
Weighted average exercise price, Options vested and exercisable	12.19
Weighted average exercise price, Vested and Expected to Vest	$ 12.49
Weighted-average remaining contractual term, Options Outstanding	7 years 2 months 12 days	7 years 6 months
Weighted-average remaining contractual term, Vested and exercisable	6 years 8 months 12 days
Weighted-average remaining contractual term, Vested and Expected to Vest	7 years 2 months 12 days
Aggregate Intrinsic Value, Options Outstanding	$ 756	$ 60,756
Aggregate Intrinsic Value, Vested and exercisable	692
Aggregate Intrinsic Value, Vested and Expected to Vest	$ 756