Stock-Based Compensation - Summary of Stock Option Activity Under Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Available for Grant, Beginning Balance	1,497,071	312,911
Shares Available for Grant, Options authorized		2,595,138
Shares Available for Grant, Options retired		(348,150)
Shares Available for Grant, Options granted	(1,069,534)	(1,124,406)
Shares Available for Grant, Options repurchased	65,984	54,128
Shares Available for Grant, Options canceled	227,400	7,450
Shares Available for Grant, Ending Balance	720,921	1,497,071	312,911
Shares Subject to Outstanding Options, Beginning Balance	1,318,647	554,669
Shares Subject to Outstanding Options, granted	1,069,534	1,124,406
Shares Subject to Outstanding Options, exercised	(18,913)	(352,978)
Shares Subject to Outstanding Options, canceled	(227,400)	(7,450)
Shares Subject to Outstanding Options, Ending Balance	2,141,868	1,318,647	554,669
Shares Subject to Outstanding Options, Options outstanding and exercisable	623,901
Shares Subject to Outstanding Options, Options vested and expected to vest	1,898,243
Weighted Average Exercise Price Per Share, Beginning Balance	$ 2.29	$ 0.43
Weighted Average Exercise Price Per Share, granted	11.57	2.80
Weighted Average Exercise Price Per Share, exercised	0.71	1.00
Weighted Average Exercise Price Per Share, repurchased	0.74	0.36
Weighted Average Exercise Price Per Share, cancelled	7.16	0.72
Weighted Average Exercise Price Per Share, Ending Balance	6.42	$ 2.29	$ 0.43
Weighted Average Exercise Price Per Share, Options outstanding and exercisable	3.28
Weighted Average Exercise Price Per Share, Options vested and expected to vest	$ 6.61
Weighted Average Remaining Contractual Term	8 years 4 months 24 days	9 years	9 years 2 months 12 days
Weighted Average Remaining Contractual Term, Options outstanding and exercisable	7 years 6 months
Weighted Average Remaining Contractual Term, Options vested and expected to vest	8 years 4 months 24 days
Aggregate Intrinsic Value, Ending Balance	$ 14,963	$ 16,305	$ 109
Aggregate Intrinsic Value, Options outstanding and exercisable, Ending Balance	6,058
Aggregate Intrinsic Value, Options vested and expected to vest, Ending Balance	$ 12,886