Finance Receivables - Summary of Loans by Internal Credit Grade (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
Retail loans
Current Period
Total	48,698	43,492
Current Period, Gross charge-offs
Total	406	293	193
Prior Year
Total	48,698	43,492
Prior Period, Gross charge-offs
Total	406	293	$ 193
Performing Financing Receivable \| Retail loans
Current Period
2025	22,105	22,174
2024	15,065	9,639
2023	6,133	5,862
2022	3,073	4,417
2021	1,868	1,153
Prior	324	296
Total	48,568	43,541
Current Period, Gross charge-offs
2025	62	58
2024	188	109
2023	88	61
2022	38	34
2021	18	19
Prior	12	12
Total	406	293
Prior Year
2024	22,105	22,174
2023	15,065	9,639
2022	6,133	5,862
2021	3,073	4,417
2020	1,868	1,153
Prior	324	296
Total	48,568	43,541
Prior Period, Gross charge-offs
2024	62	58
2023	188	109
2022	88	61
2021	38	34
2020	18	19
Prior	12	12
Total	406	293
Credit grade A \| Performing Financing Receivable \| Retail loans
Current Period
2025	14,245	14,094
2024	9,403	5,788
2023	3,620	3,713
2022	1,838	2,907
2021	1,140	597
Prior	136	121
Total	30,382	27,220
Prior Year
2024	14,245	14,094
2023	9,403	5,788
2022	3,620	3,713
2021	1,838	2,907
2020	1,140	597
Prior	136	121
Total	30,382	27,220
Credit grade B \| Performing Financing Receivable \| Retail loans
Current Period
2025	3,800	4,110
2024	2,919	2,065
2023	1,365	1,113
2022	639	778
2021	371	237
Prior	73	66
Total	9,167	8,369
Prior Year
2024	3,800	4,110
2023	2,919	2,065
2022	1,365	1,113
2021	639	778
2020	371	237
Prior	73	66
Total	9,167	8,369
Credit grade C \| Performing Financing Receivable \| Retail loans
Current Period
2025	2,830	2,853
2024	2,006	1,338
2023	869	758
2022	439	526
2021	259	200
Prior	66	61
Total	6,469	5,736
Prior Year
2024	2,830	2,853
2023	2,006	1,338
2022	869	758
2021	439	526
2020	259	200
Prior	66	61
Total	6,469	5,736
Credit grade D \| Performing Financing Receivable \| Retail loans
Current Period
2025	879	779
2024	516	306
2023	190	182
2022	103	149
2021	73	97
Prior	38	36
Total	1,799	1,549
Prior Year
2024	879	779
2023	516	306
2022	190	182
2021	103	149
2020	73	97
Prior	38	36
Total	1,799	1,549
Others \| Performing Financing Receivable \| Retail loans
Current Period
2025	351	338
2024	221	142
2023	89	96
2022	54	57
2021	25	22
Prior	11	12
Total	751	667
Prior Year
2024	351	338
2023	221	142
2022	89	96
2021	54	57
2020	25	22
Prior	11	12
Total	$ 751	$ 667

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