Stock-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended					9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Stock Options	Sep. 30, 2013 Restricted Stock Units (RSUs)	Sep. 30, 2013 LTIP	Sep. 30, 2012 LTIP	Dec. 31, 2012 LTIP	Sep. 30, 2013 LTIP Minimum	Sep. 30, 2013 LTIP Maximum	Sep. 30, 2013 Board of Directors Restricted Stock Units (RSUs)	Sep. 30, 2012 Board of Directors Restricted Stock Units (RSUs)	Dec. 31, 2012 Board of Directors Restricted Stock Units (RSUs)	May 17, 2011 2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares authorized (in shares)																1,500,000
Total compensation cost not yet recognized						$ 5,100,000	$ 9,100,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition (in years)						1 year 8 months 12 days	1 year 9 months 18 days
Share-based compensation expense	400,000	4,100,000	6,200,000	11,200,000				(1,200,000)	1,800,000				300,000	600,000
Accrued employee compensation and benefits	$ 18,063,000		$ 18,063,000		$ 22,435,000			$ 1,100,000		$ 4,500,000					$ 2,400,000
Award vesting period (in years)								3 years
Multiplier for target award based on total shareholder return on common stock (percent)											0.00%	200.00%