Stock-Based Compensation (Summary of Option Activity) (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2015
2005 Plan [Member]
Stock Options
Outstanding at January 1, 2015	16,928,098	16,928,098
Granted		22,500
Exercised		(1,286,556)
Canceled		(213,500)
Outstanding at December 31, 2015		15,450,542
Vested and expected to vest at December 31, 2015		14,948,571
Shares exercisable at December 31, 2015		8,423,167
Weighted-Average Exercise Price
Outstanding at January 1, 2015	$ 3.24	$ 3.24
Granted		6.7
Exercised		2.36
Canceled		3.79
Outstanding at December 31, 2015		3.31
Vested and expected to vest at December 31, 2015		3.25
Shares available for grant at December 31, 2015		$ 2.56
1995 Plan [Member]
Stock Options
Outstanding at January 1, 2015	35,000	35,000
Granted		0
Exercised		(35,000)
Canceled		0
Outstanding at December 31, 2015		0
Vested and expected to vest at December 31, 2015		0
Shares exercisable at December 31, 2015		0
Weighted-Average Exercise Price
Outstanding at January 1, 2015	$ 2.21	$ 2.21
Granted		0
Exercised		2.21
Canceled		0
Outstanding at December 31, 2015		0
Vested and expected to vest at December 31, 2015		0
Shares available for grant at December 31, 2015		$ 0
2015 Plan [Member]
Stock Options
Outstanding at January 1, 2015	0	0
Granted	7,014,441	8,502,941
Exercised		0
Canceled		(145,938)
Outstanding at December 31, 2015		8,357,003
Vested and expected to vest at December 31, 2015		6,812,836
Shares exercisable at December 31, 2015		280,000
Shares available for grant at December 31, 2015		16,642,997
Weighted-Average Exercise Price
Outstanding at January 1, 2015	$ 0	$ 0
Granted	$ 8.94	8.97
Exercised		0
Canceled		9.03
Outstanding at December 31, 2015		8.97
Vested and expected to vest at December 31, 2015		8.97
Shares available for grant at December 31, 2015		$ 8.97