Derivative Instruments and Hedging Activities (Interest and Amortization on Derivative Instruments) (Details) - Designated as hedging instrument - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Interest and fees on finance receivables and loans
Derivative Instruments, Gain (Loss) [Line Items]
Total gain (loss) on fair value hedging relationships	$ 53	$ (42)	$ 19	$ (128)
Interest and dividends on investment securities and other earning assets
Derivative Instruments, Gain (Loss) [Line Items]
Total gain (loss) on fair value hedging relationships	4	(2)	8	(9)
Interest on long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Total gain (loss) on fair value hedging relationships	0	(2)	1	(5)
Unsecured debt | Interest and fees on finance receivables and loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge			0	0
Unsecured debt | Interest and dividends on investment securities and other earning assets
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge			0	0
Unsecured debt | Interest on long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	1	1	3	3
Gain (loss) on interest for qualifying hedge			1	3
Federal Home Loan Bank certificates and obligations | Interest and fees on finance receivables and loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Federal Home Loan Bank certificates and obligations | Interest and dividends on investment securities and other earning assets
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Federal Home Loan Bank certificates and obligations | Interest on long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	(1)	(3)	(3)	(11)
Available-for-sale securities | Interest and fees on finance receivables and loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge	0	0	0	0
Available-for-sale securities | Interest and dividends on investment securities and other earning assets
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	4	(1)	9	(4)
Gain (loss) on interest for qualifying hedge	0	(1)	(1)	(5)
Available-for-sale securities | Interest on long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge	0	0	0	0
Fixed-rate automotive loans | Interest and fees on finance receivables and loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	17	(11)	6	(35)
Gain (loss) on interest for qualifying hedge	36	(31)	13	(93)
Fixed-rate automotive loans | Interest and dividends on investment securities and other earning assets
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge	0	0	0	0
Fixed-rate automotive loans | Interest on long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on amortization of deferred basis adjustments	0	0	0	0
Gain (loss) on interest for qualifying hedge	$ 0	$ 0	$ 0	$ 0