Servicing Activities (Schedule of Total Serviced Automobile Loans Outstanding) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Automobile Serviced Assets [Line Items]
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets	$ 64	$ 45	$ 31
Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets	64	45	$ 31
Servicing Asset	121,480	119,808
Consumer Loan [Member] | On-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	65,646	64,067
Commercial Loan [Member] | On-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	38,853	34,895
Operating Leases [Member] | On-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	11,311	15,965
Other Assets [Member] | On-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	67	72
Securitizations [Member] | Off-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	2,412	2,550
Whole-Loan Transactions [Member] | Off-Balance Sheet Loans [Member] | Automobile Loan [Member]
Automobile Serviced Assets [Line Items]
Servicing Asset	$ 3,191	$ 2,259