Income Taxes Income Taxes (Schedule of Dividends Declared Per Share) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Dividends Declared, Regular	$ 2.64	$ 2.715	$ 2.36
Taxable as Ordinary Income [Member]
Dividends Declared, Regular	$ 2.62870	$ 2.32042	$ 2.32601
Taxable as Capital Gain [Member]
Dividends Declared, Regular	$ 0.01130	$ 0.32494	$ 0.01887
Return of Capital [Member]
Dividends Declared, Regular	$ 0.00000	$ 0.06964	$ 0.01512