Derivative Instruments and Hedging Activities (Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Long-term Debt	$ 47,328	$ 44,226
Last of Layer in the Hedge Relationship	17,700
Basis Adjustment - Last-of-Layer	51
Carrying Amount [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	1,435	173
Financing Receivable, Net	41,383	2,305
Long-term Debt	14,959	14,640
Fair Value Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	(3)	2
Financing Receivable, Net	(40)	18
Long-term Debt	99	208
Discontinued Hedge [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Available-for-sale Securities, Debt Securities	(2)	2
Financing Receivable, Net	11	19
Long-term Debt	$ 95	$ 235