Equity-Based Compensation (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Equity-Based Compensation (Details)
Equity-based compensation expense	$ 6,288,000	$ 7,211,000	$ 6,662,000
Grants of restricted shares during the period, average per share market value	$ 12.43	$ 10.20	$ 8.07
Grants of restricted shares during the period, aggregate market value	4,900,000	4,400,000	800,000
Restricted shares vested during the period, aggregate fair value	$ 5,200,000	$ 2,400,000	$ 2,700,000
Restricted Stock Award Activity Detail [Table]
Nonvested restricted shares outstanding at December 31, 2010	542,000
Nonvested restricted shares as of December 31, 2010, weighted average grant date fair value per share	$ 13.92
Shares granted	397,907	434,101	98,053
Shares granted, weighted average grant date fair value per share	$ 12.43
Shares cancelled	(71,000)
Shares cancelled, weighted average grant date fair value per share	$ 13.43
Shares vested	(357,000)
Shares vested, weighted average grant date fair value per share	$ 14.56
Nonvested restricted shares outstanding at December 31, 2011	512,000	542,000
Nonvested restricted shares as of December 31, 2011, weighted average grant date fair value per share	$ 12.38	$ 13.92