Stockholder's Equity (Details 5) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Summary of dividend payments
Dividends declared and paid per common share	$ 0.795	$ 0.765
Common stock cash dividends	$ 230,801,000	$ 199,546,000
Total dividend paid	247,154,000	216,148,000
Series D Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0	$ 0.503
Preferred stock cash dividends	0	2,012,000
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.0079	$ 0.7146
Preferred stock cash dividends	1,000	250,000
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.8125	$ 0.8125
Preferred stock cash dividends	11,680,000	11,680,000
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.4064	$ 0.4064
Preferred stock cash dividends	$ 4,672,000	$ 4,672,000