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, 2018		Dec. 31, 2017		Dec. 31, 2016
Statement [Line Items]
Interest on medium- and long-term debt	$ 144	[1]	$ 76	[1]	$ 72
Swaps - fair value - receive fixed/pay floating | Risk management purposes | Interest Rate Swap [Member]
Statement [Line Items]
Interest rate contract: Hedged items interest expense	74		79
Interest rate contracts: Derivatives designated as hedging instruments net interest income	$ (7)		$ (32)

[1] Includes the effects of hedging.