Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Options (in shares):
Outstanding beginning of the period (in shares)	6,969,133
Granted (in shares)	1,194,119
Forfeited (in shares)	(251,073)
Exercised (in shares)	(322,228)
Outstanding end of the period (in shares)	7,589,951		6,969,133
Exercisable at end of the period (in shares)	4,107,422
Weighted-Average Exercise Price (in dollars per share):
Outstanding beginning of the period (in dollars per share)	$ 11.37
Granted (in dollars per share)	15.24
Forfeited (in dollars per share)	14.58
Exercised (in dollars per share)	4.22
Outstanding end of the period (in dollars per share)	12.18		$ 11.37
Exercisable at the end of the period (in dollars per share)	$ 9.69
Outstanding, weighted-average remaining contractual term (years)	7 years 4 months 24 days		7 years 8 months 12 days
Exercisable, weighted-average remaining contractual term (years)	6 years 3 months 18 days
Outstanding, aggregate intrinsic value	$ 45,209		$ 43,287
Exercisable, aggregate intrinsic value	34,677
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options exercised intrinsic value	$ 3,400	$ 5,900
Options grants in period, weighted average grant date fair value (in dollars per share)	$ 6.78	$ 6.31
Options vested in period fair value	$ 6,900	$ 6,800
Employee and Nonemployee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options unrecognized compensation expense	$ 20,400
Options unrecognized compensation expense, period for recognition (years)	2 years 6 months
Class A Common Stock | Employee and Nonemployee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Expiration period (years)	10 years
Minimum | Class A Common Stock | Employee and Nonemployee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Award vesting period (years)	3 years
Maximum | Class A Common Stock | Employee and Nonemployee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Award vesting period (years)	4 years