Advances (Advances by Year of Contractual Maturity for Convertible Advances) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Advances [Abstract]
Overdrawn demand deposit accounts	$ 1	$ 33
Due or convertible in one year or less	65,508	73,009
Due or convertible after one year through two years	13,672	13,484
Due or convertible after two years through three years	4,946	5,437
Due or convertible after three years through four years	5,078	4,642
Due or convertible after four years through five years	4,182	3,951
Due or convertible after five years	7,595	7,858
Federal Home Loan Bank, Advances, Par Value	$ 100,982	$ 108,414