Derivative Financial Instruments and Hedging Activities - Balance Sheet (Details) - Designated as Hedging Instrument [Member] - Fair Value Hedging [Member] - Unsecured Debt [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Items	$ 20,545	$ 17,923
Cumulative Amount of Fair Value Hedging Adjustments	(57)	459
Discontinued hedge cumulative amount of fair value hedging adjustments	$ 208	$ 247