Stock-Based Compensation, Nonvested Stock Option Activity (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Summary of nonvested stock activity
Granted (in shares)	1,302,298	1,348,504
Nonvested Stock Options [Member]
Summary of nonvested stock activity
Stock Options Shares Outstanding, Beginning balance (in shares)	2,438,898	2,770,662
Granted (in shares)	1,302,298	1,348,504
Vested (in shares)	(813,614)	(1,459,709)
Forfeited (in shares)	(48,190)	(220,559)
Stock Options Shares Outstanding, Ending balance (in shares)	2,879,392	2,438,898
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Exercise Price [Roll Forward]
Nonvested Weighted Average Grant Date Fair Value, Beginning balance (in usd per share)	$ 3.15	$ 3.74
Granted Weighted Average Grant Date Fair Value (in usd per share)	3.36	3.08
Vested Weighted Average Grant Date Fair Value (in usd per share)	3.25	4.19
Forfeited Weighted Average Grant Date Fair Value (in usd per share)	3.20	3.28
Nonvested Weighted Average Grant Date Fair Value, Ending balance (in usd per share)	$ 3.21	$ 3.15