Finance Receivables, Net - Schedule of Amortized Cost Basis of Retail Loan Portfolio and Dealer Products Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2025	Mar. 31, 2025
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	$ 736	$ 2,639
Year two, originated, fiscal year before current fiscal year	2,394	1,259
Year three, originated, two years before current fiscal year	1,138	711
Year four, originated, three years before current fiscal year	630	747
Year five, originated, four years before current fiscal year	713	880
Originated, more than five years before current fiscal year	1,466	810
Revolving loans	9,649	9,475
Total	16,726	16,521
Gross Charge-Offs, Total	0	0
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	7,524	32,328
Year two, originated, fiscal year before current fiscal year	30,082	24,770
Year three, originated, two years before current fiscal year	22,148	14,941
Year four, originated, three years before current fiscal year	13,126	9,505
Year five, originated, four years before current fiscal year	8,188	4,300
Originated, more than five years before current fiscal year	4,054	1,028
Total	85,122	86,872
Gross Charge-Offs, year one, originated, current fiscal year	0	31
Gross Charge-Offs, Year two, originated, fiscal year before current fiscal year	32	254
Gross Charge-Offs, Year three, originated, two years before current fiscal year	55	304
Gross Charge-Offs, Year four, originated, three years before current fiscal year	50	188
Gross Charge-Offs, Year five, originated, four years before current fiscal year	27	72
Gross Charge-Offs, Originated, more than five years before current fiscal year	14	38
Gross Charge-Offs, Total	178	887
Current [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	7,513	32,049
Year two, originated, fiscal year before current fiscal year	29,714	24,235
Year three, originated, two years before current fiscal year	21,616	14,395
Year four, originated, three years before current fiscal year	12,614	9,095
Year five, originated, four years before current fiscal year	7,814	4,094
Originated, more than five years before current fiscal year	3,802	941
Total	83,073	84,809
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	11	198
Year two, originated, fiscal year before current fiscal year	246	377
Year three, originated, two years before current fiscal year	361	384
Year four, originated, three years before current fiscal year	344	295
Year five, originated, four years before current fiscal year	260	147
Originated, more than five years before current fiscal year	169	57
Total	1,391	1,458
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	57
Year two, originated, fiscal year before current fiscal year	86	110
Year three, originated, two years before current fiscal year	123	112
Year four, originated, three years before current fiscal year	122	80
Year five, originated, four years before current fiscal year	82	41
Originated, more than five years before current fiscal year	57	18
Total	470	418
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	24
Year two, originated, fiscal year before current fiscal year	36	48
Year three, originated, two years before current fiscal year	48	50
Year four, originated, three years before current fiscal year	46	35
Year five, originated, four years before current fiscal year	32	18
Originated, more than five years before current fiscal year	26	12
Total	188	187
Wholesale [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	6,652	6,498
Total	6,652	6,498
Wholesale [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	6,251	6,042
Total	6,251	6,042
Wholesale [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	379	408
Total	379	408
Wholesale [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	12	40
Total	12	40
Wholesale [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	10	8
Total	10	8
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	540	1,814
Year two, originated, fiscal year before current fiscal year	1,673	790
Year three, originated, two years before current fiscal year	708	493
Year four, originated, three years before current fiscal year	427	592
Year five, originated, four years before current fiscal year	568	775
Originated, more than five years before current fiscal year	1,192	628
Revolving loans	43	92
Total	5,151	5,184
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	534	1,755
Year two, originated, fiscal year before current fiscal year	1,623	691
Year three, originated, two years before current fiscal year	609	485
Year four, originated, three years before current fiscal year	427	568
Year five, originated, four years before current fiscal year	539	773
Originated, more than five years before current fiscal year	1,178	596
Revolving loans	43	92
Total	4,953	4,960
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	3	55
Year two, originated, fiscal year before current fiscal year	45	89
Year three, originated, two years before current fiscal year	89	8
Year four, originated, three years before current fiscal year	0	22
Year five, originated, four years before current fiscal year	29	2
Originated, more than five years before current fiscal year	14	32
Revolving loans	0	0
Total	180	208
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	3	0
Year two, originated, fiscal year before current fiscal year	0	10
Year three, originated, two years before current fiscal year	10	0
Year four, originated, three years before current fiscal year	0	2
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	0
Total	13	12
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	4
Year two, originated, fiscal year before current fiscal year	5	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	0
Total	5	4
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	196	825
Year two, originated, fiscal year before current fiscal year	721	469
Year three, originated, two years before current fiscal year	430	218
Year four, originated, three years before current fiscal year	203	155
Year five, originated, four years before current fiscal year	145	105
Originated, more than five years before current fiscal year	274	182
Revolving loans	2,954	2,885
Total	4,923	4,839
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	166	775
Year two, originated, fiscal year before current fiscal year	720	420
Year three, originated, two years before current fiscal year	385	204
Year four, originated, three years before current fiscal year	187	152
Year five, originated, four years before current fiscal year	141	105
Originated, more than five years before current fiscal year	274	181
Revolving loans	2,863	2,789
Total	4,736	4,626
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	30	50
Year two, originated, fiscal year before current fiscal year	1	49
Year three, originated, two years before current fiscal year	45	14
Year four, originated, three years before current fiscal year	16	3
Year five, originated, four years before current fiscal year	4	0
Originated, more than five years before current fiscal year	0	1
Revolving loans	91	92
Total	187	209
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	4
Total	0	4
Working capital [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	0
Total	$ 0	$ 0