Stock Awards - Stock Options (Details) - Employee Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Stock option roll forward
Outstanding at beginning of period (in shares)	1,802,802
Granted (in shares)	1,077,013
Exercised ( in shares)	(150,230)
Canceled ( in shares)	(106,844)
Outstanding at end of period (in shares)	2,622,741	1,802,802
Exercisable at end of period (in shares)	883,660
Vested and expected to vest at end of period (in shares)	2,570,522
Weighted average exercise price
Outstanding at beginning of period (in dollars per share)	$ 5.88
Granted (in dollars per share)	19.75
Exercised ( in dollars per share)	3.60
Cancelled ( in dollars per share)	6.88
Outstanding at end of period (in dollars per share)	11.67	$ 5.88
Exercisable at end of period (in dollars per share)	6.93
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 11.56
Other disclosures
Remaining contractual life outstanding	8 years 3 months 18 days	8 years 9 months 4 days
Remaining contractual life, exercisable at end of period	7 years 7 months 21 days
Remaining contractual life, vested and expected to vest at end of period	8 years 3 months 15 days
Aggregate intrinsic value, outstanding at beginning of period	$ 37,008
Aggregate intrinsic value, outstanding at end of period	44,025	$ 37,008
Aggregate intrinsic value, exercisable at end of period	18,662
Aggregate intrinsic value, vested and expected to vest at end of period	$ 43,382
Forfeiture rate (as a percent)	2.50%