Stock-Based Compensation (Summary of Option Activity) (Details) (USD $)	6 Months Ended
	Jun. 30, 2014
2005 Stock Incentive Plan [Member]
Stock Options
Outstanding at January 1, 2014	11,788,100
Granted	5,410,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	493,462
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	225,775
Outstanding at June 30, 2014	16,478,863
Shares exercisable at June 30, 2014	6,000,837
Shares available for grant at June 30, 2014	5,416,744
Weighted-Average Exercise Price
Outstanding at January 1, 2014	$ 1.87
Granted	$ 5.59
Exercised	$ (1.87)
Canceled	$ (3.11)
Outstanding at June 30, 2014	$ 3.07
Options exercisable, June 30, 2014	$ 1.89
1995 Stock Option Plan [Member]
Stock Options
Outstanding at January 1, 2014	188,150
Granted
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	32,450
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	137,000
Outstanding at June 30, 2014	18,700
Shares exercisable at June 30, 2014	18,700
Weighted-Average Exercise Price
Outstanding at January 1, 2014	$ 5.04
Granted
Exercised	$ (4.81)
Canceled	$ (5.97)
Outstanding at June 30, 2014	$ 2.51
Options exercisable, June 30, 2014	$ 2.51