Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Summary of dividend payments
Dividends declared and paid per common share	$ 0.86	$ 0.825
Common stock cash dividends	$ 305,770	$ 272,569
Total dividends paid	$ 322,122	$ 288,921
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.8125	$ 0.8125
Preferred stock cash dividends	$ 11,680	$ 11,680
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.4064	$ 0.4064
Preferred stock cash dividends	$ 4,672	$ 4,672