Stock-based Compensation - Stock Option Activity (Details) - Employee Stock Options - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Outstanding at the beginning of the period (in shares)	1,748,875
Granted (in shares)	973,638
Exercised (in shares)	(84,127)
Cancelled or forfeited (in shares)	(61,275)
Outstanding at the end of the period (in shares)	2,577,111	1,748,875
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 15.04
Granted (in dollars per share)	33.10
Exercised (in dollars per share)	5.11
Cancelled or forfeited (in dollars per share)	22.19
Outstanding at the end of the period (in dollars per share)	$ 22.01	$ 15.04
Weighted Average
Remaining Contractual Life (Years)	8 years 9 months 15 days	9 years 4 months 17 days
Aggregate Intrinsic Value (in dollars)	$ 66,466,245	$ 8,224,947
Exercisable and Vested and Expected to Vest
Number of Shares - exercisable (in shares)	704,111	168,360
Weighted Average Exercise Price - exercisable (in dollars per share)	$ 14.86	$ 2.47
Remaining Contractual Life (Years) - exercisable	8 years 5 months 1 day	8 years 4 months 28 days
Aggregate Intrinsic Value - exercisable (in dollars)	$ 23,146,606	$ 2,907,260
Number of Shares - vested and expected to vest (in shares)	2,577,111	1,668,837
Weighted Average Exercise Price - vested and expected to vest (in dollars per share)	$ 22.01	$ 15.64
Remaining Contractual Life (Years) - vested and expected to vest	8 years 9 months 15 days	9 years 5 months 1 day
Aggregate Intrinsic Value - vested and expected to vest (in dollars)	$ 66,466,245	$ 6,842,807