Derivative Financial Instruments and Hedging Activities - Balance Sheet (Details) - Designated as Hedging Instrument [Member] - Fair Value Hedging [Member] - Unsecured Debt [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Items	$ 24,275	$ 20,397
Cumulative Amount of Fair Value Hedging Adjustments	(713)	(77)
Discontinued hedge cumulative amount of fair value hedging adjustments	$ (197)	$ 69