Stockholders' Equity (Details 8) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Options
Nonvested at beginning of period	5,090,591	5,617,554
Options granted	2,281,786	1,661,862
Options vested	(2,097,053)	(2,053,427)
Options forfeited	(73,229)	(135,398)
Nonvested at end of period	5,202,095	5,090,591	5,617,554
Weighted-Average Grant Date Fair Value
Nonvested at beginning of period (in dollars per share)	$ 3.34	$ 3.12
Options granted (in dollars per share)	3.45	4.02	$ 2.79
Options vested (in dollars per share)	3.16	3.12
Options forfeited (in dollars per share)	4.61	5.60
Nonvested at end of period (in dollars per share)	$ 3.44	$ 3.34	$ 3.12