Stock-Based Compensation (Summary of Option Activity) (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
2005 Plan [Member]
Stock Options
Outstanding at January 1, 2017	14,128,129
Granted	0
Exercised	(100,000)
Canceled	(629,325)
Outstanding at March 31, 2017	13,398,804
Shares exercisable at March 31, 2017	11,474,679
Weighted-Average Exercise Price
Outstanding at January 1, 2017 | $ / shares	$ 3.3
Granted | $ / shares	0
Exercised | $ / shares	1.24
Canceled | $ / shares	3.85
Outstanding at March 31, 2017 | $ / shares	3.29
Shares exercisable at March 31, 2017 | $ / shares	$ 3.01
2015 Plan [Member]
Stock Options
Outstanding at January 1, 2017	25,104,603
Granted	803,450
Exercised	0
Canceled	(1,123,179)
Outstanding at March 31, 2017	24,784,874
Shares exercisable at March 31, 2017	5,679,375
Shares available for grant at March 31, 2017	6,170,126
Weighted-Average Exercise Price
Outstanding at January 1, 2017 | $ / shares	$ 4.87
Granted | $ / shares	1.45
Exercised | $ / shares	0
Canceled | $ / shares	5.01
Outstanding at March 31, 2017 | $ / shares	4.75
Shares exercisable at March 31, 2017 | $ / shares	$ 7.36