Trading Securities (Major Security Types) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	$ 888	$ 915
U.S. Obligations [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	150	159
GSE Obligations [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	60	57
Other [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	259	266
Non-Mortgage-Backed Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	469	482
Multifamily [Member] | GSE MBS [Member]
Debt and Equity Securities, FV-NI [Line Items]
Trading Securities	$ 419	$ 433