Subsequent Events (Details) (Declaration of Dividends [Member], USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Subsequent Event [Line Items]
Declared date		Oct. 30, 2012
Common Stock [Member]
Subsequent Event [Line Items]
Common stock dividends declared per share	$ 0.17
Record date		Nov. 14, 2012
Payment date		Nov. 30, 2012
Series J Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared per share	$ 0.414063
Record date		Nov. 14, 2012
Payment date		Nov. 30, 2012
Series K Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared per share	$ 0.406250
Record date		Nov. 14, 2012
Payment date		Nov. 30, 2012
Series L Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared per share	$ 0.412500
Record date		Nov. 14, 2012
Payment date		Nov. 30, 2012
Series O Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividends declared per share	$ 0.523437
Record date		Dec. 17, 2012
Payment date		Dec. 31, 2012