Finance Receivables and Loans, Net Finance Receivables and Loans, Net (Consumer 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
Consumer portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	89,924,000,000	87,240,000,000
Consumer portfolio segment | California and Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.249	0.254
Consumer automotive | Consumer portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	72,390,000,000	70,539,000,000
Consumer automotive | Consumer portfolio segment | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.085	0.084
Consumer automotive | Consumer portfolio segment | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.124	0.128
Consumer automotive | Consumer portfolio segment | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.088	0.088
Consumer automotive | Consumer portfolio segment | Pennsylvania
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.046	0.045
Consumer automotive | Consumer portfolio segment | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.041	0.041
Consumer automotive | Consumer portfolio segment | Georgia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.039	0.041
Consumer automotive | Consumer portfolio segment | North Carolina
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.040	0.039
Consumer automotive | Consumer portfolio segment | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.031	0.031
Consumer automotive | Consumer portfolio segment | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.036	0.035
Consumer automotive | Consumer portfolio segment | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.028	0.027
Consumer automotive | Consumer portfolio segment | Other United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.442	0.441
Consumer automotive | Consumer portfolio segment | United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	1.000	1.000
Real estate-backed loan | Consumer portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	17,322,000,000	16,701,000,000
Real estate-backed loan | Consumer portfolio segment | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.351	0.369
Real estate-backed loan | Consumer portfolio segment | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.065	0.062
Real estate-backed loan | Consumer portfolio segment | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.051	0.047
Real estate-backed loan | Consumer portfolio segment | Pennsylvania
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.019	0.014
Real estate-backed loan | Consumer portfolio segment | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.026	0.030
Real estate-backed loan | Consumer portfolio segment | Georgia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.028	0.028
Real estate-backed loan | Consumer portfolio segment | North Carolina
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.020	0.017
Real estate-backed loan | Consumer portfolio segment | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.030	0.024
Real estate-backed loan | Consumer portfolio segment | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.005	0.004
Real estate-backed loan | Consumer portfolio segment | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.023	0.021
Real estate-backed loan | Consumer portfolio segment | Other United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	0.382	0.384
Real estate-backed loan | Consumer portfolio segment | United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance receivables and loans, net	$ 1.000	$ 1.000