Derivative And Credit-Related Financial Instruments Derivative And Credit-Related Financial Instruments (Schedule of Effects of Fair Value Hedging on the Consolidated Statements of Comprehensive Income) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement [Line Items]
Interest on medium- and long-term debt	[1]	$ 80	$ 197	$ 144
Swaps - fair value - receive fixed/pay floating | Risk management purposes | Interest Rate Swap [Member]
Statement [Line Items]
Interest rate contract: Hedged items interest expense		109	110	74
Interest rate contracts: Derivatives designated as hedging instruments net interest income		$ (51)	$ (4)	$ (7)

[1] Includes the effects of hedging.