Advances (Narrative) (Details) (USD $) In Billions, unless otherwise specified			9 Months Ended
	Sep. 30, 2012 Institutions	Dec. 31, 2011 Institutions	Sep. 30, 2012 Minimum [Member]	Sep. 30, 2012 Maximum [Member]
Advances [Line Items]
Federal Home Loan Bank Advances, Fixed Rate, Maturity Period			1 day	30 years
Federal Home Loan Bank, Advances, Floating Rate, Maturity Period			less than 30 days	10 years
Interest rate of advances			0.00%	7.40%
AHP subsidized loans, interest rate			0.00%	5.50%
Convertible Advances Outstanding	$ 2.8	$ 4.0
Federal Home Loan Bank, Advances, Returnable	6.9	1.0
Percent Of Fixed Rate Advances Swapped To Adjustable Rate	33.00%	39.10%
Percent Of Adjustable Rate Advances Swapped To Different Adjustable Rate Index	13.40%	32.70%
Federal Home Loan Bank, Advances, Five Largest Borrowers Amount Outstanding	$ 28.8	$ 20.6
Number Of Top Advances Borrowers	5	5
Federal Home Loan Bank, Advances, Five Largest Borrowers, Percent of Total	78.60%	70.40%
Federal Home Loan Bank, Advances, Borrowers With Outstanding Loan Balances Greater Than Ten Percent	4	2