Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Summary of dividend payments
Dividends declared and paid per common share	$ 0.86	$ 0.825	$ 2.58	$ 2.475
Common stock cash dividends			$ 921,381	$ 852,563
Total dividends paid			$ 970,436	$ 901,618
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	$ 35,039
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	$ 14,016