Equity and Stock Based-Compensation (Details 5) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of Distribution of Taxable Income
Common and preferred dividends paid	$ 31,556	$ 49,365	$ 55,328
Dividends treated as taxable compensation	(71)	(79)	(28)
Portion of dividends declared in current year, and paid in current year, which was applied to the prior year distribution requirements	(304)	(1,606)
Portion of dividends declared in subsequent year, and paid in subsequent year, which apply to current year distribution requirements	1,075	304	1,606
Dividends applied to meet current year REIT distribution requirements	$ 32,256	$ 47,984	$ 56,906