Finance Receivables and Loans, Net - Schedule of Loan Modifications (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($) loan	Mar. 31, 2024 USD ($) loan	Dec. 31, 2024 USD ($)
Financing Receivable, Troubled Debt Restructuring
Trial modifications, term	3 months
Trial modifications, amount	$ 5		$ 5		$ 4
Total	$ 135	$ 240
Percentage of total	0.10%	0.20%
Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	$ 6	$ 0
Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	127	228
Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	1	1
Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	0	10
Combination
Financing Receivable, Troubled Debt Restructuring
Total	1	1
Consumer
Financing Receivable, Troubled Debt Restructuring
Total	107	107	430	$ 333
Consumer | Current
Financing Receivable, Troubled Debt Restructuring
Total			332	272
Consumer | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			62	40
Consumer | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			23	11
Consumer | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			13	10
Consumer | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Consumer | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	105	99
Consumer | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	1	1
Consumer | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	0	6
Consumer | Combination
Financing Receivable, Troubled Debt Restructuring
Total	1	1
Consumer | Automotive
Financing Receivable, Troubled Debt Restructuring
Total	106	100	$ 427	$ 315
Number of loans redefaulted | loan			1,858	481
Amortized cost of loans redefaulted			$ 46	$ 11
Consumer | Automotive | Current
Financing Receivable, Troubled Debt Restructuring
Total			330	259
Consumer | Automotive | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			62	39
Consumer | Automotive | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			23	10
Consumer | Automotive | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			12	7
Consumer | Automotive | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0
Payment extensions, number of months extended/deferred	29 months	29 months
Consumer | Automotive | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	$ 105	$ 99	420	303
Consumer | Automotive | Contractual maturity extensions | Current
Financing Receivable, Troubled Debt Restructuring
Total			328	253
Consumer | Automotive | Contractual maturity extensions | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			62	38
Consumer | Automotive | Contractual maturity extensions | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			23	10
Consumer | Automotive | Contractual maturity extensions | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			7	2
Consumer | Automotive | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	1	1	5	12
Principal forgiveness, amount forgiven	0	0
Consumer | Automotive | Principal forgiveness | Current
Financing Receivable, Troubled Debt Restructuring
Total			0	6
Consumer | Automotive | Principal forgiveness | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	1
Consumer | Automotive | Principal forgiveness | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Automotive | Principal forgiveness | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			5	5
Consumer | Automotive | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Consumer | Automotive | Combination
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0	2
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Consumer | Automotive | Combination | Current
Financing Receivable, Troubled Debt Restructuring
Total			2
Consumer | Automotive | Combination | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0
Consumer | Automotive | Combination | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0
Consumer | Automotive | Combination | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			0
Consumer | Consumer mortgage finance receivables
Financing Receivable, Troubled Debt Restructuring
Total	$ 1	$ 1	3	4
Consumer | Consumer mortgage finance receivables | Current
Financing Receivable, Troubled Debt Restructuring
Total			2	4
Consumer | Consumer mortgage finance receivables | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			1	0
Consumer | Consumer mortgage finance receivables | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Consumer | Consumer mortgage finance receivables | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	0	0	2	2
Consumer | Consumer mortgage finance receivables | Contractual maturity extensions | Current
Financing Receivable, Troubled Debt Restructuring
Total			1	2
Consumer | Consumer mortgage finance receivables | Contractual maturity extensions | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | Contractual maturity extensions | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | Contractual maturity extensions | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			1	0
Consumer | Consumer mortgage finance receivables | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Principal forgiveness, amount forgiven	0	0
Consumer | Consumer mortgage finance receivables | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Consumer | Consumer mortgage finance receivables | Combination
Financing Receivable, Troubled Debt Restructuring
Total	$ 1	$ 1	1	2
Interest rate concessions, initial rate	4.50%	3.50%
Interest rate concessions, revised rate	2.80%	3.40%
Payment extensions, initial term	291 months	355 months
Payment extensions, revised term	480 months	480 months
Consumer | Consumer mortgage finance receivables | Combination | Current
Financing Receivable, Troubled Debt Restructuring
Total			1	2
Consumer | Consumer mortgage finance receivables | Combination | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | Combination | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Consumer mortgage finance receivables | Combination | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Consumer | Other
Financing Receivable, Troubled Debt Restructuring
Total		$ 6		14
Consumer | Other | Current
Financing Receivable, Troubled Debt Restructuring
Total				9
Consumer | Other | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total				1
Consumer | Other | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total				1
Consumer | Other | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total				3
Consumer | Other | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total		0
Consumer | Other | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total		0
Consumer | Other | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total		0
Principal forgiveness, amount forgiven		0
Consumer | Other | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total		$ 6		14
Interest rate concessions, initial rate		30.50%
Interest rate concessions, revised rate		10.10%
Consumer | Other | Interest rate concessions | Current
Financing Receivable, Troubled Debt Restructuring
Total				9
Consumer | Other | Interest rate concessions | 30–59 days past due
Financing Receivable, Troubled Debt Restructuring
Total				1
Consumer | Other | Interest rate concessions | 60–89 days past due
Financing Receivable, Troubled Debt Restructuring
Total				1
Consumer | Other | Interest rate concessions | 90 or more days past due
Financing Receivable, Troubled Debt Restructuring
Total				3
Consumer | Other | Combination
Financing Receivable, Troubled Debt Restructuring
Total		$ 0
Interest rate concessions, initial rate		0.00%
Interest rate concessions, revised rate		0.00%
Commercial
Financing Receivable, Troubled Debt Restructuring
Total	$ 28	$ 133	73	171
Commercial | Pass
Financing Receivable, Troubled Debt Restructuring
Total			25	107
Commercial | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Commercial | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			44	64
Commercial | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			4	0
Commercial | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	$ 6	$ 0
Payment extensions, number of months extended/deferred	15 months	41 months
Commercial | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	$ 22	$ 129
Commercial | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Principal forgiveness, amount forgiven	0	0
Commercial | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 4
Interest rate concessions, initial rate	0.00%	12.90%
Interest rate concessions, revised rate	0.00%	11.50%
Commercial | Combination
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Commercial | Automotive
Financing Receivable, Troubled Debt Restructuring
Total	$ 2	$ 4
Commercial | Automotive | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	$ 2	0	4
Payment extensions, number of months extended/deferred	7 months
Commercial | Automotive | Payment deferrals | Pass
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Payment deferrals | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Payment deferrals | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			4
Commercial | Automotive | Payment deferrals | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	0
Commercial | Automotive | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Principal forgiveness, amount forgiven	0	0
Commercial | Automotive | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 4		4
Interest rate concessions, initial rate	0.00%	12.90%
Interest rate concessions, revised rate	0.00%	11.50%
Commercial | Automotive | Interest rate concessions | Pass
Financing Receivable, Troubled Debt Restructuring
Total				0
Commercial | Automotive | Interest rate concessions | Special mention
Financing Receivable, Troubled Debt Restructuring
Total				0
Commercial | Automotive | Interest rate concessions | Substandard
Financing Receivable, Troubled Debt Restructuring
Total				4
Commercial | Automotive | Interest rate concessions | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total				0
Commercial | Automotive | Combination
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0	3
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Commercial | Automotive | Combination | Pass
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Combination | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Combination | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Automotive | Combination | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			3
Commercial | Other
Financing Receivable, Troubled Debt Restructuring
Total	$ 26	$ 129
Commercial | Other | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total	$ 4	$ 0	4
Payment extensions, number of months extended/deferred	16 months	41 months
Commercial | Other | Payment deferrals | Pass
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Other | Payment deferrals | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Other | Payment deferrals | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			4
Commercial | Other | Payment deferrals | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Other | Contractual maturity extensions
Financing Receivable, Troubled Debt Restructuring
Total	$ 22	$ 129	47	167
Commercial | Other | Contractual maturity extensions | Pass
Financing Receivable, Troubled Debt Restructuring
Total			25	107
Commercial | Other | Contractual maturity extensions | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0	0
Commercial | Other | Contractual maturity extensions | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			22	60
Commercial | Other | Contractual maturity extensions | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			0	$ 0
Commercial | Other | Principal forgiveness
Financing Receivable, Troubled Debt Restructuring
Total	0	0
Principal forgiveness, amount forgiven	0	0
Commercial | Other | Interest rate concessions
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Commercial | Other | Combination
Financing Receivable, Troubled Debt Restructuring
Total	$ 0	$ 0	14
Interest rate concessions, initial rate	0.00%	0.00%
Interest rate concessions, revised rate	0.00%	0.00%
Commercial | Other | Combination | Pass
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Other | Combination | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Other | Combination | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			14
Commercial | Other | Combination | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Commercial real estate | Payment deferrals
Financing Receivable, Troubled Debt Restructuring
Total			1
Commercial | Commercial real estate | Payment deferrals | Pass
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Commercial real estate | Payment deferrals | Special mention
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Commercial real estate | Payment deferrals | Substandard
Financing Receivable, Troubled Debt Restructuring
Total			0
Commercial | Commercial real estate | Payment deferrals | Doubtful
Financing Receivable, Troubled Debt Restructuring
Total			$ 1