Stock-Based Awards - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Options, Number of Shares
Number of Shares, beginning balance	1,738,524	500,262
Number of Shares, Granted	1,083,919	1,238,262	500,262
Number of Shares, Exercised	(51,980)
Number of Shares, Forfeited and canceled	(68,113)
Number of Shares, ending balance	2,702,350	1,738,524	500,262
Number of Shares, Options vested and expected to vest	2,702,350
Number of Shares, Options exercisable	575,149
Options, Weighted Average Exercise Price
Weighted Average Exercise Price, beginning balance (in dollars per share)	$ 13.23	$ 1.22
Weighted Average Exercise Price, Granted (in dollars per share)	27.12	18.08	$ 1.22
Weighted Average Exercise Price, Exercised (in dollars per share)	2.37
Weighted Average Exercise Price, Forfeited and canceled (in dollars per share)	15.71
Weighted Average Exercise Price, ending balance (in dollars per share)	18.94	$ 13.23	$ 1.22
Weighted Average Exercise Price, Options vested and expected to vest (in dollars per share)	18.94
Weighted Average Exercise Price, Options exercisable (in dollars per share)	$ 10.93
Options, Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	9 years 18 days	9 years 6 months 4 days	9 years 9 months 7 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in years)	9 years 18 days
Weighted Average Remaining Contractual Term, Options exercisable (in years)	8 years 5 months 1 day
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 24,434	$ 24,722	$ 305
Aggregate Intrinsic Value, Options vested and expected to vest	24,434
Aggregate Intrinsic Value, Options exercisable	$ 9,512
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 21.16	$ 13.84	$ 1.38