Stockholder's Equity (Details 5) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Summary of dividend payments
Dividends declared and paid per common share	$ 0.87	$ 0.87
Common stock cash dividends	$ 323,726	$ 315,415
Total dividends paid	$ 335,402	$ 329,794
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.8125	$ 0.8125
Preferred stock cash dividends	$ 11,676	$ 11,680
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0	$ 0.2347
Preferred stock cash dividends	$ 0	$ 2,699