Advances (Advances by Interest Rate Payment Terms) (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Advances [Abstract]
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Fixed Rate	[1]	$ 32,407,774	$ 24,700,450
Federal Home Loan Bank Advances, Maturities by Interest Rate Type, Floating Rate	[1]	38,704,706	45,206,571
Federal Home Loan Bank, Advances, Par Value, Total		$ 71,112,480	$ 69,907,021

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