Equity-Based Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity-Based Compensation (Details)
Equity-based compensation expense	$ 9,441,000	$ 6,288,000	$ 7,211,000
Grants of restricted shares during the period, aggregate market value	3,600,000	4,900,000	4,400,000
Restricted shares vested during the period, aggregate fair value	$ 4,800,000	$ 5,200,000	$ 2,400,000
Restricted Stock Award Activity Detail [Table]
Nonvested restricted shares outstanding at December 31, 2011	512,000
Nonvested restricted shares at December 31, 2011, weighted average grant date fair value per share	$ 12.38
Shares granted	523,096	397,907	434,101
Shares granted, weighted average grant date fair value per share	$ 6.83	$ 12.43	$ 10.2
Shares cancelled	(57,000)
Shares cancelled, weighted average grant date fair value per share	$ 10.78
Shares vested	(357,000)
Shares vested, weighted average grant date fair value per share	$ 11.25
Nonvested restricted shares outstanding at December 31, 2012	621,000	512,000
Nonvested restricted shares at December 31, 2012, weighted average grant date fair value per share	$ 8.49	$ 12.38
Unit Award Activity Detail
Nonvested units outstanding at December 31, 2011	160,000
Nonvested units at December 31, 2011, weighted average grant date fair value per unit	$ 17.87
Units granted	95,000
Units granted, weighted average grant date fair value per unit	$ 13.68
Units cancelled	(5,000)
Units cancelled, weighted average grant date fair value per share	$ 17.29
Units vested	(69,000)
Units vested, weighted average grant date fair value per unit	$ 17.48
Nonvested units outstanding at December 31, 2012	181,000	160,000
Nonvested units at December 31, 2012, weighted average grant date fair value per unit	$ 15.84	$ 17.87