Stock-Based Compensation (Summary of Option Activity) (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance, Outstanding, Number of Options (shares) | shares	10,711,321
Granted, Number of Options (shares) | shares	233,123
Exercised, Number of Options (shares) | shares	(128,969)
Forfeited, Number of Options (shares) | shares	(88,022)
Expired, Number of Options (shares) | shares	(12,808)
Ending Balance, Outstanding, Number of Options (shares) | shares	10,714,645
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning Balance, Outstanding, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 6.16
Granted, Weighted-Average Exercise Price (in dollars per share) | $ / shares	7.57
Exercised, Weighted-Average Exercise Price (in dollars per share) | $ / shares	0.56
Forfeited, Weighted-Average Exercise Price (in dollars per share) | $ / shares	10.87
Expired, Weighted-Average Exercise Price (in dollars per share) | $ / shares	10.64
Ending Balance, Outstanding, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 6.21
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, Weighted-Average Remaining Contractual Term	7 years 7 months 22 days
Outstanding, Aggregate Intrinsic Value | $	$ 37,652
Exercisable, Number of Options (shares) | shares	5,581,014
Exercisable, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 3.51
Exercisable, Weighted-Average Remaining Contractual Term	6 years 11 months 10 days
Exercisable, Aggregate Intrinsic Value | $	$ 29,147
Vested or expected to vest, Number of Options (shares) | shares	10,475,409
Vested or expected to vest, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 6.10
Vested or expected to vest, Weighted-Average Remaining Contractual Term	7 years 7 months 22 days
Vested or expected to vest, Aggregate Intrinsic Value | $	$ 37,509