Finance Receivables and Loans, Net Finance Receivables and Loans, Net (Commercial Concentration Risk) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	$ 128,231,000,000	$ 129,926,000,000
Commercial portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	38,307,000,000	42,686,000,000
Commercial portfolio segment | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.150	0.155
Commercial portfolio segment | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.116	0.116
Commercial portfolio segment | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.082	0.068
Commercial portfolio segment | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.072	0.083
Commercial portfolio segment | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.059	0.048
Commercial portfolio segment | North Carolina
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.046	0.036
Commercial portfolio segment | Georgia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.035	0.040
Commercial portfolio segment | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.029	0.031
Commercial portfolio segment | South Carolina
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.028	0.034
Commercial portfolio segment | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.024	0.020
Commercial portfolio segment | Other United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.359	0.369
Commercial portfolio segment | United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	$ 1.000	$ 1.000