Stockholder's Equity (Details 3) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of dividend payments
Dividends declared and paid per common share	$ 3.3	$ 3.18	$ 3.06
Common stock cash dividends	$ 1,144,727	$ 969,661	$ 839,939
Total dividend paid	$ 1,210,133	$ 1,035,069	$ 906,275
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 0	$ 0.00794	$ 2.8584
Preferred stock cash dividends	$ 0	$ 1	$ 930
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 3.25	$ 3.25	$ 3.25
Preferred stock cash dividends	$ 46,719	$ 46,719	$ 46,719
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 1.6251	$ 1.6251	$ 1.6251
Preferred stock cash dividends	$ 18,687	$ 18,688	$ 18,687