Advances Interest Rate Payment Terms (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Advances by Interest Rate Payment Terms [Line Items]
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Fixed Rate, under One Year	$ 7,932,949	$ 7,979,254
Federal Home Loan Bank Advances Maturities Summary by Interest Rate Type Fixed Rate After One Year	7,393,427	7,883,320
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Fixed Rate	15,326,376	15,862,574
Federal Home Loan Bank, Advances, Maturities by Interest Rate Type, Floating Rate, under One Year	1,041,672	1,016,682
Federal Home Loan Bank Advances Maturities Summary by Interest Rate Type Floating Rate After One Year	44,000	1,049,000
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Floating Rate	1,085,672	2,065,682
Federal Home Loan Bank Advances Par Value	$ 16,412,048	$ 17,928,256