Advances (Advances by Interest Rate Payment Terms) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Advances [Abstract]
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Fixed Rate, under One Year	$ 4,395,475	[1]	$ 9,412,060	[1]
Federal Home Loan Bank Advances Maturities Summary by Interest Rate Type Fixed Rate After One Year	8,127,141	[1]	8,224,609	[1]
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Fixed Rate	12,522,616	[1]	17,636,669	[1]
Federal Home Loan Bank, Advances, Maturities by Interest Rate Type, Floating Rate, under One Year	1,224,789	[1]	2,363,338	[1]
Federal Home Loan Bank Advances Maturities Summary by Interest Rate Type Floating Rate After One Year	44,251,647	[1]	33,620,771	[1]
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Floating Rate	45,476,436	[1]	35,984,109	[1]
Federal Home Loan Bank Advances At Par Value	$ 57,999,052		$ 53,620,778

[1] Payment terms based on current interest rate terms, which would reflect any option exercises or rate conversions subsequent to the related Advance issuance.