Stockholder's Equity (Details 5) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Summary of dividend payments
Dividends declared and paid per common share	$ 0.765	$ 0.74	$ 2.295	$ 2.22
Common stock cash dividends			$ 618,992,000	$ 460,936,000
Total dividend paid			668,797,000	513,463,000
Series D Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0	$ 0.503
Preferred stock cash dividends			0	2,012,000
Series F Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0	$ 0.4872
Preferred stock cash dividends			0	3,410,000
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 2.1438	$ 2.1438
Preferred stock cash dividends			750,000	750,000
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 2.4375	$ 2.4375
Preferred stock cash dividends			35,039,000	35,039,000
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.2189	$ 0.9841
Preferred stock cash dividends			$ 14,016,000	$ 11,316,000