Capital (Excess Capital Stock) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital [Line Items]
Mandatorily redeemable capital stock		$ 138	$ 227	$ 309	$ 457
Amount of Excess Stock Repurchased During Period		$ 1,224	1,753
Common stock, par value		$ 100
Excess Capital		$ 197	166
Excess Capital Stock and Excess Mandatorily Redeemable Capital Stock, Redemption, Period of Written Notice		15 days
Mandatorily Redeemable Capital Stock, Redemption Period		5 years
Interest Expense on Mandatorily Redeemable Capital Stock	[1]	$ 14	$ 24	$ 32
Maximum
Capital [Line Items]
Dividends, Cash Declared, Annualized Rate		7.00%
Minimum
Capital [Line Items]
Dividends, Cash Declared, Annualized Rate		5.00%

[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