Preferred Stock (Details Textual) (USD $)			6 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Series F [Member]	Jan. 23, 2012 Series F [Member]	Jun. 30, 2012 Series G [Member]	Apr. 20, 2012 Series G [Member]
Preferred Stock (Textual) [Abstract]
Preferred Stock, Shares Issued			44,000		43,400
Liquidation preference per share				$ 25,000		$ 25,000
Preferred stock, dividend rate, period			Three month LIBOR plus		Three month LIBOR plus
Preferred stock, dividend rate, variable percentage			4.468%		4.86125%
Maximum period to redeem preferred stock			90 days		90 days
Preferred stock, dividend rate, fixed percentage			6.50%		6.00%
Preferred Stock (Additional Textual) [Abstract]
Number of preferred stock shares authorized	50,000,000	50,000,000
Par value of Preference shares issued and outstanding	$ 1.00	$ 1.00