Stockholder's Equity (Details Textual) (USD $)	9 Months Ended				9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Series I cumulative convertible perpetual preferred stock [Member]	Sep. 30, 2011 Series I cumulative convertible perpetual preferred stock [Member] 6.50% Series [Member]	Sep. 30, 2010 Series G Preferred Stock [Member]	Sep. 30, 2011 Other Equity	Sep. 30, 2010 Other Equity	Sep. 30, 2011 Other Equity	Sep. 30, 2010 Other Equity
Stockholders' Equity [Line Items]
Cumulative Convertible Preferred Stock, Converted Into common Stock						394,200
Common stock issued on conversion of preferred stock						282,078
Cumulative Convertible Preferred Stock, Outstanding	25,724,854		11,349,854			5,513
Cumulative convertible perpetual preferred stock issued					14,375,000
Liquidation value per preferred share				$ 50.00
Preferred stock dividend percentage					6.50%	7.50%
Equivalent Number Of Common Stock On Conversion Of Preferred Shares	84.60%
Initial conversion price	$ 59.10
Other equity	$ 1,641,000	$ 1,414,000					$ 301,000	$ 221,000	$ 1,641,000	$ 1,414,000