Finance Receivables - Summary of Loans by Internal Credit Grade (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Mar. 31, 2026
Current Period
Total	$ 55,446		$ 54,876
Current Period, Gross charge-offs
Total	113	$ 102
Prior Year
Total	55,446		54,876
Prior Period, Gross charge-offs
Total	113	102
Retail loans
Current Period
Total	50,750		50,173
Current Period, Gross charge-offs
Total	113	102
Prior Year
Total	50,750		50,173
Prior Period, Gross charge-offs
Total	113	$ 102
Performing \| Retail loans
Current Period
2027	6,573		20,768
2026	18,779		14,967
2025	13,294		9,202
2024	7,929		3,426
2023	2,868		1,236
Prior	1,199		477
Total	50,642		50,076
Current Period, Gross charge-offs
2027	0		63
2026	41		204
2025	39		141
2024	21		55
2023	8		19
Prior	4		11
Total	113		493
Prior Year
2026	6,573		20,768
2025	18,779		14,967
2024	13,294		9,202
2023	7,929		3,426
2022	2,868		1,236
Prior	1,199		477
Total	50,642		50,076
Prior Period, Gross charge-offs
2026	0		63
2025	41		204
2024	39		141
2023	21		55
2022	8		19
Prior	4		11
Total	113		493
Performing \| Retail loans \| Credit grade A
Current Period
2027	4,372		13,406
2026	12,010		9,504
2025	8,420		5,625
2024	4,810		1,948
2023	1,609		659
Prior	613		243
Total	31,834		31,385
Prior Year
2026	4,372		13,406
2025	12,010		9,504
2024	8,420		5,625
2023	4,810		1,948
2022	1,609		659
Prior	613		243
Total	31,834		31,385
Performing \| Retail loans \| Credit grade B
Current Period
2027	1,080		3,659
2026	3,368		2,696
2025	2,418		1,879
2024	1,636		808
2023	686		295
Prior	290		113
Total	9,478		9,450
Prior Year
2026	1,080		3,659
2025	3,368		2,696
2024	2,418		1,879
2023	1,636		808
2022	686		295
Prior	290		113
Total	9,478		9,450
Performing \| Retail loans \| Credit grade C
Current Period
2027	796		2,664
2026	2,454		1,954
2025	1,742		1,255
2024	1,099		510
2023	438		208
Prior	212		82
Total	6,741		6,673
Prior Year
2026	796		2,664
2025	2,454		1,954
2024	1,742		1,255
2023	1,099		510
2022	438		208
Prior	212		82
Total	6,741		6,673
Performing \| Retail loans \| Credit grade D
Current Period
2027	249		767
2026	702		584
2025	513		307
2024	266		109
2023	92		49
Prior	56		28
Total	1,878		1,844
Prior Year
2026	249		767
2025	702		584
2024	513		307
2023	266		109
2022	92		49
Prior	56		28
Total	1,878		1,844
Performing \| Retail loans \| Others
Current Period
2027	76		272
2026	245		229
2025	201		136
2024	118		51
2023	43		25
Prior	28		11
Total	711		724
Prior Year
2026	76		272
2025	245		229
2024	201		136
2023	118		51
2022	43		25
Prior	28		11
Total	$ 711		$ 724

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