Stockholder's Equity (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary of dividend payments
Dividends declared and paid per common share	$ 0.765	$ 0.74	$ 1.53	$ 1.48
Common stock cash dividends			$ 399,815	$ 301,503
Total dividend paid			433,018	337,429
Series D Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0	$ 0.9844
Preferred stock cash dividends			0	2,013
Series F Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0	$ 0.9532
Preferred stock cash dividends			0	3,410
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.4292	$ 1.4292
Preferred stock cash dividends			500	500
Series I Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 1.6250	$ 1.6250
Preferred stock cash dividends			23,359	23,359
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share			$ 0.8126	$ 0.5778
Preferred stock cash dividends			$ 9,344	$ 6,644