Derivative Financial Instruments and Hedging Activities - Derivatives Recognized in the Balance Sheet (Details) - Designated as Hedging Instrument [Member] - Fair Value Hedging [Member] - Unsecured Debt [Member] $ in Millions	Sep. 30, 2018 USD ($)
Derivatives, Fair Value [Line Items]
Carrying Amount of Hedged Items	$ 15,363
Cumulative Amount of Fair Value Hedging Adjustments	735
Discontinued hedge cumulative amount of fair value hedging adjustments	$ 178