Capital (Mandatorily Redeemable Capital Stock) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2019 USD ($) Institutions	Dec. 31, 2018 USD ($) Institutions	Dec. 31, 2017 USD ($)
Capital [Line Items]
Financial Instruments Subject to Mandatory Redemption, Number of Stockholders | Institutions		3	3
Interest Expense on Mandatorily Redeemable Capital Stock	[1]	$ 14	$ 24	$ 32
Mandatorily Redeemable Capital Stock [Roll Forward]
Balance at the beginning of the period		227	309	457
Reclassified from/(to) capital during the period		6	2	2
Financial Instruments Subject to Mandatory Redemption, Redemption		0	0	(75)
Repurchase of excess mandatorily redeemable capital stock		(95)	(84)	(75)
Balance at the end of the period		$ 138	$ 227	$ 309

[1] The Bank excludes interest expense on mandatorily redeemable capital stock from adjusted net interest income in its analysis of financial performance for its two operating segments