Stock-Based Awards - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Options, Number of Shares
Number of Shares, beginning balance	2,702,350
Number of Shares, Granted	617,500
Number of Shares, Exercised	(36,738)
Number of Shares, Forfeited and cancelled	(40,281)
Number of Shares, ending balance	3,242,831	2,702,350
Number of Shares, Options vested and expected to vest	3,242,831
Number of Shares, Options exercisable	828,823
Options, Weighted Average Exercise Price
Weighted Average Exercise Price, beginning balance (in dollars per share)	$ 18.94
Weighted Average Exercise Price, Granted (in dollars per share)	26.47
Weighted Average Exercise Price, Exercised (in dollars per share)	6.40
Weighted Average Exercise Price, Forfeited and cancelled (in dollars per share)	21.09
Weighted Average Exercise Price, ending balance (in dollars per share)	20.49	$ 18.94
Weighted Average Exercise Price, Options vested and expected to vest (in dollars per share)	20.49
Weighted Average Exercise Price, Options exercisable (in dollars per share)	$ 10.95
Options, Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	8 years 7 months 6 days	9 years 18 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest (in years)	8 years 7 months 6 days
Weighted Average Remaining Contractual Term, Options exercisable (in years)	7 years 8 months 23 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 21,704	$ 24,434
Aggregate Intrinsic Value, Options vested and expected to vest	21,704
Aggregate Intrinsic Value, Options exercisable	$ 12,666
Weighted average grant-date fair value of stock options granted (in dollars per share)	$ 20.41