Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Summary of dividend payments
Dividends declared and paid per common share	$ 0.87	$ 0.86	$ 2.61	$ 2.58
Common stock cash dividends			$ 955,631	$ 921,381
Total dividends paid			$ 993,365	$ 970,436
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 2.4375	$ 2.4375
Preferred stock cash dividends			$ 35,035	$ 35,039
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0.2347	$ 1.2189
Preferred stock cash dividends			$ 2,699	$ 14,016