Finance Receivables and Loans, Net (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	$ 1,439		$ 1,522	$ 1,036
Financing Receivable, Nonaccrual, No Allowance	692		706
Financing Receivable, Nonaccrual, Interest Income	2	$ 2
Consumer portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	1,270		1,361	821
Financing Receivable, Nonaccrual, No Allowance	604		650
Consumer portfolio segment | Automotive loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	1,173		1,256	762
Financing Receivable, Nonaccrual, No Allowance	554		604
Consumer portfolio segment | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	95		102	57
Financing Receivable, Nonaccrual, No Allowance	50		46
Consumer portfolio segment | Mortgage Finance operations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	63		67	17
Financing Receivable, Nonaccrual, No Allowance	23		18
Consumer portfolio segment | Mortgage - Legacy
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	32		35	40
Financing Receivable, Nonaccrual, No Allowance	27		28
Consumer portfolio segment | Other loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	2		3	2
Financing Receivable, Nonaccrual, No Allowance	0		0
Commercial portfolio segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	169		161	215
Financing Receivable, Nonaccrual, No Allowance	88		56
Commercial portfolio segment | Automotive loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	17		40	73
Financing Receivable, Nonaccrual, No Allowance	1		10
Commercial portfolio segment | Real estate-backed loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	2		5	4
Financing Receivable, Nonaccrual, No Allowance	2		5
Commercial portfolio segment | Other loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	150		116	$ 138
Financing Receivable, Nonaccrual, No Allowance	$ 85		$ 41