Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary of dividend payments
Dividends declared and paid per common share	$ 0.87	$ 0.86	$ 1.74	$ 1.72
Common stock cash dividends			$ 634,296	$ 613,163
Total dividends paid			$ 660,355	$ 645,866
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.625	$ 1.625
Preferred stock cash dividends			$ 23,360	$ 23,359
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0.2347	$ 0.8126
Preferred stock cash dividends			$ 2,699	$ 9,344