Finance Receivables - Summary of Loans by Risk Rate Grouping (Detail) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Current Period
Total	$ 53,042	$ 47,552
Current Period, Gross charge-offs
Total	406	293	$ 193
Prior Year
Total	53,042	47,552
Prior Period, Gross charge-offs
Total	406	293	193
Dealer loans
Current Period
Total	4,344	4,060
Current Period, Gross charge-offs
Total	0	0	0
Prior Year
Total	4,344	4,060
Prior Period, Gross charge-offs
Total	0	0	$ 0
Dealer loans \| Performing Financing Receivable
Current Period
Total	4,344	4,060
Current Period, Gross charge-offs
Total	0	0
Prior Year
Total	4,344	4,060
Prior Period, Gross charge-offs
Total	0	0
Dealer loans \| Group I \| Performing Financing Receivable
Current Period
Total	2,989	3,075
Prior Year
Total	2,989	3,075
Dealer loans \| Group II \| Performing Financing Receivable
Current Period
Total	1,354	984
Prior Year
Total	1,354	984
Dealer loans \| Group III \| Performing Financing Receivable
Current Period
Total	1	1
Prior Year
Total	1	1
Dealer loans \| Commercial loans \| Performing Financing Receivable
Current Period
2025	172	190
2024	166	58
2023	55	14
2022	13	115
2021	92	45
Prior	78	104
Revolving loans	762	748
Current Period, Gross charge-offs
2025	0	0
2024	0	0
2023	0	0
2022	0	0
2021	0	0
Prior	0	0
Revolving loans	0	0
Prior Year
2024	172	190
2023	166	58
2022	55	14
2021	13	115
2020	92	45
Prior	78	104
Revolving loans	762	748
Prior Period, Gross charge-offs
2024	0	0
2023	0	0
2022	0	0
2021	0	0
2020	0	0
Prior	0	0
Revolving loans	0	0
Dealer loans \| Commercial loans \| Group I \| Performing Financing Receivable
Current Period
2025	149	146
2024	110	55
2023	52	9
2022	13	114
2021	86	45
Prior	53	84
Revolving loans	762	748
Prior Year
2024	149	146
2023	110	55
2022	52	9
2021	13	114
2020	86	45
Prior	53	84
Revolving loans	762	748
Dealer loans \| Commercial loans \| Group II \| Performing Financing Receivable
Current Period
2025	23	44
2024	56	3
2023	3	5
2022	0	1
2021	6	0
Prior	25	20
Revolving loans	0	0
Prior Year
2024	23	44
2023	56	3
2022	3	5
2021	0	1
2020	6	0
Prior	25	20
Revolving loans	0	0
Dealer loans \| Commercial loans \| Group III \| Performing Financing Receivable
Current Period
2025	0	0
2024	0	0
2023	0	0
2022	0	0
2021	0	0
Prior	0	0
Revolving loans	0	0
Prior Year
2024	0	0
2023	0	0
2022	0	0
2021	0	0
2020	0	0
Prior	0	0
Revolving loans	0	0
Dealer loans \| Wholesale flooring \| Performing Financing Receivable
Current Period
Total	3,006	2,786
Current Period, Gross charge-offs
Total	0	0
Prior Year
Total	3,006	2,786
Prior Period, Gross charge-offs
Total	0	0
Dealer loans \| Wholesale flooring \| Group I \| Performing Financing Receivable
Current Period
Total	1,764	1,874
Prior Year
Total	1,764	1,874
Dealer loans \| Wholesale flooring \| Group II \| Performing Financing Receivable
Current Period
Total	1,241	911
Prior Year
Total	1,241	911
Dealer loans \| Wholesale flooring \| Group III \| Performing Financing Receivable
Current Period
Total	1	1
Prior Year
Total	$ 1	$ 1

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Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

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