Shareholders' Equity of the REIT (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common share distributions and preferred share dividends
Ordinary income	$ 0.07		$ 1.30
Qualified dividend	$ 0.01		$ 0.20
Capital gains	$ 0.84	$ 1.25	$ 0.07
Return of capital	$ 0.14
Total dividend	$ 1.06	$ 1.25	$ 1.57
Series L Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.15
Capital gains	$ 1.07
Total dividend	$ 1.22
Series M Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.15
Capital gains	$ 1.11
Total dividend	$ 1.26
Series O Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.16
Capital gains	$ 1.15
Total dividend	$ 1.31
Series P Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.15
Capital gains	$ 1.13
Total dividend	$ 1.28
Series Q Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.38		$ 3.56
Qualified dividend	$ 0.04		$ 0.54
Capital gains	$ 3.85	$ 4.27	$ 0.17
Total dividend	$ 4.27	$ 4.27	$ 4.27
Series R Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.15		$ 1.41
Qualified dividend	$ 0.02		$ 0.21
Capital gains	$ 1.52	$ 1.69	$ 0.07
Total dividend	$ 1.69	$ 1.69	$ 1.69
Series S Preferred Stock [Member]
Common share distributions and preferred share dividends
Ordinary income	$ 0.15		$ 1.41
Qualified dividend	$ 0.02		$ 0.21
Capital gains	$ 1.52	$ 1.69	$ 0.07
Total dividend	$ 1.69	$ 1.69	$ 1.69