Stockholders' Equity (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividend/Distribution per Share/ Unit, common stock									$ 0.00	$ 0.00	$ 0.00
Total Dividend/Distribution, preferred stock	$ 4,763	$ 4,928	$ 4,947	$ 4,927	$ 4,854	$ 4,884	$ 4,979	$ 4,960	$ 19,565	$ 19,677	$ 19,516
Series F Preferred Stock [Member]
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividend/Distribution per Share/ Unit, preferred stock									$ 6,511	$ 6,736	$ 6,415
Total Dividend/Distribution, preferred stock									3,256	3,368	3,207
Series G Preferred Stock [Member]
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividend/Distribution per Share/ Unit, preferred stock									$ 7,236	$ 7,236	$ 7,236
Total Dividend/Distribution, preferred stock									1,809	1,809	1,809
Series J Preferred Stock [Member]
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividend/Distribution per Share/ Unit, preferred stock									$ 18,125	$ 18,125	$ 18,125
Total Dividend/Distribution, preferred stock									10,875	10,875	10,875
Series K Preferred Stock [Member]
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Dividend/Distribution per Share/ Unit, preferred stock									$ 18,125	$ 18,125	$ 18,125
Total Dividend/Distribution, preferred stock									$ 3,625	$ 3,625	$ 3,625