Finance Receivables and Loans, Net (Schedule of Pass And Criticized Credit Quality Indicators of Finance Receivables) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	$ 130,055	$ 129,926	$ 125,327
Commercial portfolio segment | Commercial loan
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	40,844	42,686	$ 41,326
Commercial portfolio segment | Commercial loan | Pass
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	37,011	38,710
Commercial portfolio segment | Commercial loan | Criticized
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	3,833	3,976
Commercial portfolio segment | Commercial and industrial automotive
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	31,559	33,672
Commercial portfolio segment | Commercial and industrial automotive | Pass
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	28,774	30,799
Commercial portfolio segment | Commercial and industrial automotive | Criticized
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	2,785	2,873
Commercial portfolio segment | Commercial and industrial other
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	4,516	4,205
Commercial portfolio segment | Commercial and industrial other | Pass
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	3,711	3,373
Commercial portfolio segment | Commercial and industrial other | Criticized
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	805	832
Commercial portfolio segment | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	4,769	4,809
Commercial portfolio segment | Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	4,526	4,538
Commercial portfolio segment | Commercial real estate | Criticized
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	$ 243	$ 271