Summary Of Significant Accounting Policies (Tax Treatment Of Common Dividends Per Share For Federal Tax Purposes) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Line Items]
Dividends, treatment for federal tax purposes	$ 2.11	$ 2.00	$ 2.36
Dividends, treatment for federal tax purposes (percent)	100.00%	100.00%	100.00%
Ordinary Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Dividends, treatment for federal tax purposes	$ 2.06	$ 1.17	$ 2.15
Dividends, treatment for federal tax purposes (percent)	97.39%	58.39%	90.93%
Capital Gain Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Dividends, treatment for federal tax purposes	$ 0.05
Dividends, treatment for federal tax purposes (percent)	2.61%
Return Of Capital [Member]
Summary Of Significant Accounting Policies [Line Items]
Dividends, treatment for federal tax purposes		$ 0.83	$ 0.21
Dividends, treatment for federal tax purposes (percent)		41.61%	9.07%