Subsequent Events (Details) (USD $)	0 Months Ended	12 Months Ended
	Feb. 04, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Subsequent Events [Abstract]
Common stock dividends declared per share	$ 0.66	$ 2.48	$ 2.32	$ 2.68
Approved dividend distribution on the UPREIT Units		$ 0.66
Dividend record date	Feb. 16, 2012
Dividend payable date	Feb. 28, 2012