Stock-Based Compensation - Stock Option Activity (Details) - Employee Stock Options - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Number of Shares
Outstanding at the beginning of the period (in shares)	1,748,877
Granted (in shares)	877,640
Exercised (in shares)	33,625	138,000
Cancelled or forfeited (in shares)	25,875
Outstanding at the end of the period (in shares)	2,567,017		1,748,877
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 15.04
Granted (in dollars per share)	31.41
Exercised (in dollars per share)	6.50
Cancelled or forfeited (in dollars per share)	18.17
Outstanding at the end of the period (in dollars per share)	$ 20.51		$ 15.04
Weighted Average
Remaining Contractual Life (Years)	8 years 11 months 12 days		9 years 4 months 17 days
Aggregate Intrinsic Value (in dollars)	$ 54,745,699		$ 8,224,947
Exercisable and Vested and Expected to Vest
Number of Shares - exercisable (in shares)	635,347
Weighted Average Exercise Price - exercisable (in dollars per share)	$ 13.54
Number of Shares - vested and expected to vest (in shares)	2,502,817
Weighted Average Exercise Price - vested and expected to vest (in dollars per share)	$ 21.17
Remaining Contractual Life (Years) - vested and expected to vest	8 years 11 months 23 days
Aggregate Intrinsic Value - vested and expected to vest (in dollars)	$ 50,563,537