Finance Receivables - Summary of Loans by Internal Credit Grade (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2025
Current Period
Total	$ 54,887		$ 53,042
Current Period, Gross charge-offs
Total	102	$ 79
Prior Year
Total	54,887		53,042
Prior Period, Gross charge-offs
Total	102	79
Retail loans
Current Period
Total	50,302		48,698
Current Period, Gross charge-offs
Total	102	79
Prior Year
Total	50,302		48,698
Prior Period, Gross charge-offs
Total	102	$ 79
Performing \| Retail loans
Current Period
2026	6,799		22,105
2025	20,273		15,065
2024	13,507		6,133
2023	5,404		3,073
2022	2,537		1,868
Prior	1,604		324
Total	50,124		48,568
Current Period, Gross charge-offs
2026	0		62
2025	43		188
2024	37		88
2023	14		38
2022	5		18
Prior	3		12
Total	102		406
Prior Year
2025	6,799		22,105
2024	20,273		15,065
2023	13,507		6,133
2022	5,404		3,073
2021	2,537		1,868
Prior	1,604		324
Total	50,124		48,568
Prior Period, Gross charge-offs
2025	0		62
2024	43		188
2023	37		88
2022	14		38
2021	5		18
Prior	3		12
Total	102		406
Credit grade A \| Performing \| Retail loans
Current Period
2026	4,499		14,245
2025	12,987		9,403
2024	8,406		3,620
2023	3,171		1,838
2022	1,485		1,140
Prior	908		136
Total	31,456		30,382
Prior Year
2025	4,499		14,245
2024	12,987		9,403
2023	8,406		3,620
2022	3,171		1,838
2021	1,485		1,140
Prior	908		136
Total	31,456		30,382
Credit grade B \| Performing \| Retail loans
Current Period
2026	1,137		3,800
2025	3,531		2,919
2024	2,643		1,365
2023	1,216		639
2022	544		371
Prior	337		73
Total	9,408		9,167
Prior Year
2025	1,137		3,800
2024	3,531		2,919
2023	2,643		1,365
2022	1,216		639
2021	544		371
Prior	337		73
Total	9,408		9,167
Credit grade C \| Performing \| Retail loans
Current Period
2026	815		2,830
2025	2,622		2,006
2024	1,797		869
2023	768		439
2022	374		259
Prior	246		66
Total	6,622		6,469
Prior Year
2025	815		2,830
2024	2,622		2,006
2023	1,797		869
2022	768		439
2021	374		259
Prior	246		66
Total	6,622		6,469
Credit grade D \| Performing \| Retail loans
Current Period
2026	252		879
2025	810		516
2024	460		190
2023	169		103
2022	88		73
Prior	85		38
Total	1,864		1,799
Prior Year
2025	252		879
2024	810		516
2023	460		190
2022	169		103
2021	88		73
Prior	85		38
Total	1,864		1,799
Others \| Performing \| Retail loans
Current Period
2026	96		351
2025	323		221
2024	201		89
2023	80		54
2022	46		25
Prior	28		11
Total	774		751
Prior Year
2025	96		351
2024	323		221
2023	201		89
2022	80		54
2021	46		25
Prior	28		11
Total	$ 774		$ 751

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