Stock-Based Compensation, Nonvested Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of nonvested stock activity
Granted (in shares)	1,348,504	1,389,452	1,020,979
Nonvested Stock Options [Member]
Summary of nonvested stock activity
Stock Options Shares Outstanding, Beginning balance (in shares)	2,770,662	3,110,523	4,036,595
Granted (in shares)	1,348,504	1,389,452	1,020,979
Vested (in shares)	(1,459,709)	(1,522,152)	(1,680,981)
Forfeited (in shares)	(220,559)	(207,161)	(266,070)
Stock Options Shares Outstanding, Ending balance (in shares)	2,438,898	2,770,662	3,110,523
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)	$ 3.74	$ 4.69	$ 5.11
Granted Weighted Average Grant Date Fair Value (in usd per share)	3.08	3.00	3.80
Vested Weighted Average Grant Date Fair Value (in usd per share)	4.19	4.92	5.10
Forfeited Weighted Average Grant Date Fair Value (in usd per share)	3.28	4.38	5.05
Nonvested Weighted Average Grant Date Fair Value, Ending balance (in usd per share)	$ 3.15	$ 3.74	$ 4.69