Derivative And Credit-Related Financial Instruments Derivative and Credit-Related Financial Instruments (Schedule of the Effects of Fair Value Hedging on the Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Total interest on medium- and long-term debt	[1]	$ 40	$ 19	$ 97	$ 56
Swaps - fair value - receive fixed/pay floating | Risk management purposes | Interest rate swap
Interest rate contract: Hedge items interest expense		21	19	51	64
Interest rate contracts: Derivatives designated as hedging instruments net interest income		$ (1)	$ (7)	$ (7)	$ (27)

[1] Includes the effects of hedging.