Stock-Based Compensation (Summary of Option Activity) (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance, Outstanding, Number of Options (in shares) | shares	10,711,321
Granted, Number of Options (in shares) | shares	447,732
Exercised, Number of Options (in shares) | shares	(253,894)
Forfeited, Number of Options (in shares) | shares	(171,103)
Expired, Number of Options (in shares) | shares	(41,913)
Ending Balance, Outstanding, Number of Options (in shares) | shares	10,692,143
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning Balance, Outstanding, Weighted-Average Exercise Price (USD per share) | $ / shares	$ 6.16
Granted, Weighted-Average Exercise Price (USD per share) | $ / shares	6.24
Exercised, Weighted-Average Exercise Price (USD per share) | $ / shares	0.50
Forfeited, Weighted-Average Exercise Price (USD per share) | $ / shares	9.76
Expired, Weighted-Average Exercise Price (USD per share) | $ / shares	12.91
Ending Balance, Outstanding, Weighted-Average Exercise Price (USD per share) | $ / shares	$ 6.20
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, Weighted-Average Remaining Contractual Term (in years)	7 years 5 months 19 days
Outstanding, Aggregate Intrinsic Value | $	$ 22,984
Exercisable, Number of Options (in shares) | shares	6,010,981
Exercisable, Weighted-Average Exercise Price (USD per share) | $ / shares	$ 3.80
Exercisable, Weighted-Average Remaining Contractual Term (in years)	6 years 9 months 18 days
Exercisable, Aggregate Intrinsic Value | $	$ 19,104
Vested or expected to vest, Number of Options (in shares) | shares	10,509,124
Vested or expected to vest, Weighted-Average Exercise Price (USD per share) | $ / shares	$ 6.11
Vested or expected to vest, Weighted-Average Remaining Contractual Term (in years)	7 years 5 months 19 days
Vested or expected to vest, Aggregate Intrinsic Value | $	$ 22,935