Finance Receivables and Loans, Net (Past Due Financing Receivables and Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	$ 3,144	$ 3,151
Financing receivable, recorded investment, current	125,465	126,775
Total finance receivables and loans	128,609	129,926	$ 126,605
Consumer portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	3,077	3,098
Financing receivable, recorded investment, current	87,004	84,142
Total finance receivables and loans	90,081	87,240
Consumer portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,890	2,940
Financing receivable, recorded investment, current	70,181	67,599
Total finance receivables and loans	73,071	70,539	69,995
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	187	158
Financing receivable, recorded investment, current	16,823	16,543
Total finance receivables and loans	17,010	16,701	16,506
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	123	76
Financing receivable, recorded investment, current	15,659	15,079
Total finance receivables and loans	15,782	15,155
Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	64	82
Financing receivable, recorded investment, current	1,164	1,464
Total finance receivables and loans	1,228	1,546
Commercial portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	67	53
Financing receivable, recorded investment, current	38,461	42,633
Total finance receivables and loans	38,528	42,686	$ 40,104
Commercial portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	46	32
Financing receivable, recorded investment, current	29,076	33,640
Total finance receivables and loans	29,122	33,672
Commercial portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	3	1
Financing receivable, recorded investment, current	5,026	4,808
Total finance receivables and loans	5,029	4,809
Commercial portfolio segment | Other loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	18	20
Financing receivable, recorded investment, current	4,359	4,185
Total finance receivables and loans	4,377	4,205
Financing receivables, 30 to 59 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,191	2,204
Financing receivables, 30 to 59 days past due | Consumer portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,188	2,204
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2,053	2,107
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	135	97
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	107	67
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	28	30
Financing receivables, 30 to 59 days past due | Commercial portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	3	0
Financing receivables, 30 to 59 days past due | Commercial portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1	0
Financing receivables, 30 to 59 days past due | Commercial portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	2	0
Financing receivables, 30 to 59 days past due | Commercial portfolio segment | Other loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Financing receivables, 60 to 89 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	535	557
Financing receivables, 60 to 89 days past due | Consumer portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	535	552
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	521	537
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	14	15
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	6	5
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	8	10
Financing receivables, 60 to 89 days past due | Commercial portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	5
Financing receivables, 60 to 89 days past due | Commercial portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	1
Financing receivables, 60 to 89 days past due | Commercial portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	0
Financing receivables, 60 to 89 days past due | Commercial portfolio segment | Other loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	0	4
Financing receivables, equal to greater than 90 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	418	390
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	354	342
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	316	296
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	38	46
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	10	4
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	28	42
Financing receivables, equal to greater than 90 days past due | Commercial portfolio segment
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	64	48
Financing receivables, equal to greater than 90 days past due | Commercial portfolio segment | Automotive loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	45	31
Financing receivables, equal to greater than 90 days past due | Commercial portfolio segment | Real estate-backed loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	1	1
Financing receivables, equal to greater than 90 days past due | Commercial portfolio segment | Other loan
Financing Receivable, Past Due [Line Items]
Financing receivable, recorded investment, past due	$ 18	$ 16