Transfers of Receivables - Exposure Based on Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	$ 670	$ 935
Fair Value of Derivative Liabilities	663	310
Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	70	121
Fair Value of Derivative Liabilities	49	31
Related to Variable Interest Entity - Not VIE [Member] | Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	12	23
Fair Value of Derivative Liabilities	11	29
Other, Not Variable Interest Entity Related [Member] | Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	31	34
Fair Value of Derivative Liabilities	14	0
Variable Interest Entity, Primary Beneficiary [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	27	64
Fair Value of Derivative Liabilities	24	2
Variable Interest Entity, Primary Beneficiary [Member] | Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	27	64
Fair Value of Derivative Liabilities	$ 24	$ 2