Stockholders' Equity (Deficit) (Summary of Activity Related to Stock Options) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of options outstanding, Beginning balance	1,859,970	1,946,823
Number of options outstanding, Granted	1,249,683	1,385,370
Number of options outstanding, Exercised	(292,581)	(1,287,883)
Number of options outstanding, Expired or Canceled	0	0
Number of options outstanding, Forfeited	(70,677)	(184,340)
Number of options outstanding, Ending balance	2,746,395	1,859,970	1,946,823
Number of options outstanding, Exercisable	1,035,166
Number of options outstanding, Vested and expected to vest	2,691,231
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average exercise price, Beginning balance (in USD per share)	$ 15.79	$ 3.54
Weighted-average exercise price, Granted (in USD per share)	41.80	21.57
Weighted-average exercise price, Exercised (in USD per share)	7.22	3.57
Weighted-average exercise price, Expired or Canceled (in USD per share)	0.00	0.00
Weighted-average exercise price, Forfeited (in USD per share)	30.78	15.30
Weighted-average exercise price, Ending balance (in USD per share)	28.19	$ 15.79	$ 3.54
Weighted-average exercise price, Exercisable (in USD per share)	21.13
Weighted-average exercise price, Vested or expected to vest (in USD per share)	$ 28.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual life (in years), Beginning	8 years 149 days	8 years 5 months 16 days	7 years 11 days
Weighted-average remaining contractual life (in years), Exercisable	7 years 288 days
Weighted-average remaining contractual life (in years), Vested or expected to vest	8 years 146 days
Aggregate intrinsic value of options outstanding	$ 1,964,237
Aggregate intrinsic value of options exercisable	1,588,756
Aggregate intrinsic value of options vested or expected to vest	$ 1,952,766