Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Summary of dividend payments
Dividends declared and paid per common share	$ 0.86	$ 0.825	$ 1.72	$ 1.65
Common stock cash dividends			$ 613,163	$ 561,914
Total dividends paid			$ 645,866	$ 594,617
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.625	$ 1.625
Preferred stock cash dividends			$ 23,359	$ 23,359
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0.8126	$ 0.8126
Preferred stock cash dividends			$ 9,344	$ 9,344