Derivative Instruments and Hedging Activities (Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Long-term Debt	$ 45,076	$ 44,226
Last of Layer in the Hedge Relationship	9,700
Basis Adjustment - Last-of-Layer	45
Carrying Amount [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	985	173
Financing Receivable, Net	22,121	2,305
Long-term Debt	14,958	14,640
Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	0	2
Financing Receivable, Net	(31)	18
Long-term Debt	127	208
Discontinued Hedge [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	2	2
Financing Receivable, Net	14	19
Long-term Debt	$ 163	$ 235