Stockholder's Equity (Details 5) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Summary of dividend payments
Dividends declared and paid per common share	$ 0.765	$ 0.740
Common stock cash dividends	$ 199,546	$ 142,919
Total dividend paid	216,148	162,126
Series D Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0	$ 0.4922
Preferred stock cash dividends	0	1,969
Series F Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0	$ 0.4766
Preferred stock cash dividends	0	3,336
Series H Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.7146	$ 0.3750
Preferred stock cash dividends	250	250
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	11,680
Series J Preferred Stock [Member]
Summary of dividend payments
Dividends declared and paid per preferred share	$ 0.4064	$ 0.1715
Preferred stock cash dividends	$ 4,672	$ 1,972