Finance Receivables, Net - Schedule of Amortized Cost Basis of Retail Loan Portfolio and Dealer Products Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	$ 2,639	$ 2,083
Year two, originated, fiscal year before current fiscal year	1,259	1,381
Year three, originated, two years before current fiscal year	711	1,117
Year four, originated, three years before current fiscal year	747	1,026
Year five, originated, four years before current fiscal year	880	235
Originated, more than five years before current fiscal year	810	945
Revolving loans	9,475	9,394
Total	16,521	16,181
Gross Charge-Offs, Total	0	0
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	32,328	35,823
Year two, originated, fiscal year before current fiscal year	24,770	23,173
Year three, originated, two years before current fiscal year	14,941	15,639
Year four, originated, three years before current fiscal year	9,505	8,878
Year five, originated, four years before current fiscal year	4,300	2,783
Originated, more than five years before current fiscal year	1,028	829
Total	86,872	87,125
Gross Charge-Offs, year one, originated, current fiscal year	31	38
Gross Charge-Offs, Year two, originated, fiscal year before current fiscal year	254	297
Gross Charge-Offs, Year three, originated, two years before current fiscal year	304	258
Gross Charge-Offs, Year four, originated, three years before current fiscal year	188	111
Gross Charge-Offs, Year five, originated, four years before current fiscal year	72	38
Gross Charge-Offs, Originated, more than five years before current fiscal year	38	34
Gross Charge-Offs, Total	887	776
Current [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	32,049	35,407
Year two, originated, fiscal year before current fiscal year	24,235	22,473
Year three, originated, two years before current fiscal year	14,395	15,041
Year four, originated, three years before current fiscal year	9,095	8,539
Year five, originated, four years before current fiscal year	4,094	2,654
Originated, more than five years before current fiscal year	941	748
Total	84,809	84,862
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	198	301
Year two, originated, fiscal year before current fiscal year	377	488
Year three, originated, two years before current fiscal year	384	426
Year four, originated, three years before current fiscal year	295	242
Year five, originated, four years before current fiscal year	147	92
Originated, more than five years before current fiscal year	57	53
Total	1,458	1,602
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	57	77
Year two, originated, fiscal year before current fiscal year	110	143
Year three, originated, two years before current fiscal year	112	119
Year four, originated, three years before current fiscal year	80	68
Year five, originated, four years before current fiscal year	41	27
Originated, more than five years before current fiscal year	18	17
Total	418	451
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	24	38
Year two, originated, fiscal year before current fiscal year	48	69
Year three, originated, two years before current fiscal year	50	53
Year four, originated, three years before current fiscal year	35	29
Year five, originated, four years before current fiscal year	18	10
Originated, more than five years before current fiscal year	12	11
Total	187	210
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	6,498	6,673
Total	6,498	6,673
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	6,042	6,287
Total	6,042	6,287
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	408	238
Total	408	238
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	40	112
Total	40	112
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	8	36
Total	8	36
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	1,814	1,294
Year two, originated, fiscal year before current fiscal year	790	923
Year three, originated, two years before current fiscal year	493	869
Year four, originated, three years before current fiscal year	592	891
Year five, originated, four years before current fiscal year	775	128
Originated, more than five years before current fiscal year	628	786
Revolving loans	92	3
Total	5,184	4,894
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	1,755	1,224
Year two, originated, fiscal year before current fiscal year	691	883
Year three, originated, two years before current fiscal year	485	815
Year four, originated, three years before current fiscal year	568	860
Year five, originated, four years before current fiscal year	773	128
Originated, more than five years before current fiscal year	596	784
Revolving loans	92	3
Total	4,960	4,697
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	55	58
Year two, originated, fiscal year before current fiscal year	89	37
Year three, originated, two years before current fiscal year	8	44
Year four, originated, three years before current fiscal year	22	6
Year five, originated, four years before current fiscal year	2	0
Originated, more than five years before current fiscal year	32	0
Revolving loans	0	0
Total	208	145
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	8
Year two, originated, fiscal year before current fiscal year	10	1
Year three, originated, two years before current fiscal year	0	10
Year four, originated, three years before current fiscal year	2	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	2
Revolving loans	0	0
Total	12	21
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	4	4
Year two, originated, fiscal year before current fiscal year	0	2
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	25
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	4	31
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	825	789
Year two, originated, fiscal year before current fiscal year	469	458
Year three, originated, two years before current fiscal year	218	248
Year four, originated, three years before current fiscal year	155	135
Year five, originated, four years before current fiscal year	105	107
Originated, more than five years before current fiscal year	182	159
Revolving loans	2,885	2,718
Total	4,839	4,614
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	775	769
Year two, originated, fiscal year before current fiscal year	420	414
Year three, originated, two years before current fiscal year	204	235
Year four, originated, three years before current fiscal year	152	122
Year five, originated, four years before current fiscal year	105	105
Originated, more than five years before current fiscal year	181	159
Revolving loans	2,789	2,715
Total	4,626	4,519
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	50	20
Year two, originated, fiscal year before current fiscal year	49	41
Year three, originated, two years before current fiscal year	14	13
Year four, originated, three years before current fiscal year	3	0
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	1	0
Revolving loans	92	2
Total	209	76
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	3
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	2
Originated, more than five years before current fiscal year	0	0
Revolving loans	4	1
Total	4	6
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	13
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	$ 13