Company-Obligated Mandatorily Redeemable Capital Securities (Details) (USD $)			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Floating Rate Junior Subordinated Deferrable Interest Debentures [Member]	Mar. 31, 2013 Floating Rate Capital Securities [Member]	Sep. 21, 2006 Floating Rate Capital Securities [Member]
Class of Stock [Line Items]
Face amount of capital securities					$ 4,000,000
Capital securities, basis spread on variable rate (in hundredths)				1.70%
Capital securities, description of variable rate basis				three month LIBOR
Capital securities	4,124,000	4,124,000
Callable period of capital securities				5 years
Debt Instrument [Line Items]
Principal amount of debt			$ 4,000,000
Maturity date			Dec. 31, 2036