Stockholder's Equity (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Summary of dividend payments
Dividends declared and paid per common share	$ 3.06	$ 2.96	$ 2.835
Common stock cash dividends	$ 839,939,000	$ 653,321,000	$ 483,746,000
Total dividend paid	906,275,000	722,450,000	544,248,000
Series D Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 0	$ 0.50301	$ 1.96875
Preferred stock cash dividends	0	2,012,000	7,875,000
Series F Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 0	$ 0.48715	$ 1.90625
Preferred stock cash dividends	0	3,410,000	13,344,000
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 2.8584	$ 2.8584	$ 2.8584
Preferred stock cash dividends	930,000	1,000,000	1,000,000
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 3.25	$ 3.25	$ 1.33159
Preferred stock cash dividends	46,719,000	46,719,000	38,283,000
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per Preferred share	$ 1.6251	$ 1.39038	$ 0
Preferred stock cash dividends	$ 18,687,000	$ 15,988,000	$ 0