Common Stock Dividends (Schedule of Dividends Declared Per Share) (Details) (USD $)	Jan. 31, 2012		Dec. 31, 2011	Nov. 10, 2011	Aug. 10, 2011	May 10, 2011
Dividends declared per common share	$ 0.870	[1]	$ 2.715	$ 0.615	$ 0.615	$ 0.615
Taxable as Ordinary Income [Member]
Dividends declared per common share	$ 0.743559	[1]	$ 2.320416	$ 0.525619	$ 0.525619	$ 0.525619
Taxable as Capital Gain [Member]
Dividends declared per common share	$ 0.104125	[1]	$ 0.324943	$ 0.073606	$ 0.073606	$ 0.073606
Return of Capital [Member]
Dividends declared per common share	$ 0.022316	[1]	$ 0.069641	$ 0.015775	$ 0.015775	$ 0.015775

[1] Declared for stockholders of record on December 31, 2011