Finance Receivables - Summary of Loans by Internal Credit Grade (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024	Mar. 31, 2025
Current Period
Total	$ 54,767		$ 54,767		$ 53,042
Current Period, Gross charge-offs
Total	131	$ 111	362	$ 287
Prior Year
Total	54,767		54,767		53,042
Prior Period, Gross charge-offs
Total	131	111	362	287
Retail loans
Current Period
Total	50,264		50,264		48,698
Current Period, Gross charge-offs
Total	131	111	362	287
Prior Year
Total	50,264		50,264		48,698
Prior Period, Gross charge-offs
Total	131	$ 111	362	$ 287
Performing \| Retail loans
Current Period
2026	16,495		16,495		22,105
2025	16,702		16,702		15,065
2024	10,568		10,568		6,133
2023	4,036		4,036		3,073
2022	1,620		1,620		1,868
Prior	753		753		324
Total	50,174		50,174		48,568
Current Period, Gross charge-offs
2026			27		62
2025			157		188
2024			110		88
2023			43		38
2022			15		18
Prior			10		12
Total			362		406
Prior Year
2025	16,495		16,495		22,105
2024	16,702		16,702		15,065
2023	10,568		10,568		6,133
2022	4,036		4,036		3,073
2021	1,620		1,620		1,868
Prior	753		753		324
Total	50,174		50,174		48,568
Prior Period, Gross charge-offs
2025			27		62
2024			157		188
2023			110		88
2022			43		38
2021			15		18
Prior			10		12
Total			362		406
Credit grade A \| Performing \| Retail loans
Current Period
2026	10,609		10,609		14,245
2025	10,641		10,641		9,403
2024	6,510		6,510		3,620
2023	2,325		2,325		1,838
2022	898		898		1,140
Prior	395		395		136
Total	31,378		31,378		30,382
Prior Year
2025	10,609		10,609		14,245
2024	10,641		10,641		9,403
2023	6,510		6,510		3,620
2022	2,325		2,325		1,838
2021	898		898		1,140
Prior	395		395		136
Total	31,378		31,378		30,382
Credit grade B \| Performing \| Retail loans
Current Period
2026	2,899		2,899		3,800
2025	2,972		2,972		2,919
2024	2,123		2,123		1,365
2023	934		934		639
2022	371		371		371
Prior	173		173		73
Total	9,472		9,472		9,167
Prior Year
2025	2,899		2,899		3,800
2024	2,972		2,972		2,919
2023	2,123		2,123		1,365
2022	934		934		639
2021	371		371		371
Prior	173		173		73
Total	9,472		9,472		9,167
Credit grade C \| Performing \| Retail loans
Current Period
2026	2,126		2,126		2,830
2025	2,175		2,175		2,006
2024	1,425		1,425		869
2023	590		590		439
2022	259		259		259
Prior	127		127		66
Total	6,702		6,702		6,469
Prior Year
2025	2,126		2,126		2,830
2024	2,175		2,175		2,006
2023	1,425		1,425		869
2022	590		590		439
2021	259		259		259
Prior	127		127		66
Total	6,702		6,702		6,469
Credit grade D \| Performing \| Retail loans
Current Period
2026	628		628		879
2025	655		655		516
2024	354		354		190
2023	127		127		103
2022	61		61		73
Prior	43		43		38
Total	1,868		1,868		1,799
Prior Year
2025	628		628		879
2024	655		655		516
2023	354		354		190
2022	127		127		103
2021	61		61		73
Prior	43		43		38
Total	1,868		1,868		1,799
Others \| Performing \| Retail loans
Current Period
2026	233		233		351
2025	259		259		221
2024	156		156		89
2023	60		60		54
2022	31		31		25
Prior	15		15		11
Total	754		754		751
Prior Year
2025	233		233		351
2024	259		259		221
2023	156		156		89
2022	60		60		54
2021	31		31		25
Prior	15		15		11
Total	$ 754		$ 754		$ 751

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