Stockholder's Equity (Details 5) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Summary of dividend payments
Dividends declared and paid per common share	$ 0.825	$ 0.795	$ 2.475	$ 2.385
Common stock cash dividends			$ 852,563,000	$ 708,923,000
Total dividends paid			$ 901,618,000	$ 757,980,000
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share				$ 0.0079
Preferred stock cash dividends				$ 1,000
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	$ 35,040,000
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.2189	$ 1.2189
Preferred stock cash dividends			$ 14,016,000	$ 14,016,000