Finance Receivables, Net - Schedule of Amortized Cost Basis of Retail Loan Portfolio and Dealer Products Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Millions	Sep. 30, 2021	Mar. 31, 2021
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	$ 1,038	$ 2,400
Year two, originated, fiscal year before current fiscal year	1,858	703
Year three, originated, two years before current fiscal year	559	805
Year four, originated, three years before current fiscal year	713	431
Year five, originated, four years before current fiscal year	382	455
Originated, more than five years before current fiscal year	1,912	1,804
Revolving loans	3,488	7,044
Total	9,950	13,642
Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	17,994	32,228
Year two, originated, fiscal year before current fiscal year	27,464	16,249
Year three, originated, two years before current fiscal year	12,660	9,127
Year four, originated, three years before current fiscal year	6,768	6,090
Year five, originated, four years before current fiscal year	4,288	2,497
Originated, more than five years before current fiscal year	1,615	537
Total	70,789	66,728
Current [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	17,865	32,026
Year two, originated, fiscal year before current fiscal year	27,058	16,047
Year three, originated, two years before current fiscal year	12,422	8,972
Year four, originated, three years before current fiscal year	6,604	5,977
Year five, originated, four years before current fiscal year	4,172	2,435
Originated, more than five years before current fiscal year	1,527	496
Total	69,648	65,953
30-59 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	99	147
Year two, originated, fiscal year before current fiscal year	290	145
Year three, originated, two years before current fiscal year	172	114
Year four, originated, three years before current fiscal year	119	83
Year five, originated, four years before current fiscal year	84	46
Originated, more than five years before current fiscal year	59	27
Total	823	562
60-89 Days Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	21	37
Year two, originated, fiscal year before current fiscal year	79	39
Year three, originated, two years before current fiscal year	46	28
Year four, originated, three years before current fiscal year	32	21
Year five, originated, four years before current fiscal year	22	11
Originated, more than five years before current fiscal year	18	8
Total	218	144
90 Days or Greater Past Due [Member] | Retail Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	9	18
Year two, originated, fiscal year before current fiscal year	37	18
Year three, originated, two years before current fiscal year	20	13
Year four, originated, three years before current fiscal year	13	9
Year five, originated, four years before current fiscal year	10	5
Originated, more than five years before current fiscal year	11	6
Total	100	69
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	2,913	6,157
Total	2,913	6,157
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	2,893	5,893
Total	2,893	5,893
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	8	218
Total	8	218
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	35
Total	12	35
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	0	11
Total	0	11
Real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	734	1,895
Year two, originated, fiscal year before current fiscal year	1,441	369
Year three, originated, two years before current fiscal year	326	599
Year four, originated, three years before current fiscal year	541	389
Year five, originated, four years before current fiscal year	340	342
Originated, more than five years before current fiscal year	1,678	1,609
Revolving loans	0	0
Total	5,060	5,203
Real estate [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	712	1,874
Year two, originated, fiscal year before current fiscal year	1,426	320
Year three, originated, two years before current fiscal year	326	596
Year four, originated, three years before current fiscal year	541	356
Year five, originated, four years before current fiscal year	340	312
Originated, more than five years before current fiscal year	1,640	1,493
Revolving loans	0	0
Total	4,985	4,951
Real estate [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	8
Year two, originated, fiscal year before current fiscal year	2	49
Year three, originated, two years before current fiscal year	0	3
Year four, originated, three years before current fiscal year	0	20
Year five, originated, four years before current fiscal year	0	9
Originated, more than five years before current fiscal year	13	99
Revolving loans	0	0
Total	15	188
Real estate [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	9	13
Year two, originated, fiscal year before current fiscal year	13	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	12
Originated, more than five years before current fiscal year	25	17
Revolving loans	0	0
Total	47	42
Real estate [Member] | Default [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	13	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	9
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	0
Total	13	22
Working capital [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	304	505
Year two, originated, fiscal year before current fiscal year	417	334
Year three, originated, two years before current fiscal year	233	206
Year four, originated, three years before current fiscal year	172	42
Year five, originated, four years before current fiscal year	42	113
Originated, more than five years before current fiscal year	234	195
Revolving loans	575	887
Total	1,977	2,282
Working capital [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	304	503
Year two, originated, fiscal year before current fiscal year	415	334
Year three, originated, two years before current fiscal year	233	200
Year four, originated, three years before current fiscal year	172	41
Year five, originated, four years before current fiscal year	42	106
Originated, more than five years before current fiscal year	234	176
Revolving loans	575	878
Total	1,975	2,238
Working capital [Member] | Credit Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	1
Year two, originated, fiscal year before current fiscal year	1	0
Year three, originated, two years before current fiscal year	0	6
Year four, originated, three years before current fiscal year	0	1
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	0	19
Revolving loans	0	9
Total	1	36
Working capital [Member] | At Risk [Member]
Financing Receivable, Recorded Investment [Line Items]
Year one, originated, current fiscal year	0	1
Year two, originated, fiscal year before current fiscal year	1	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	7
Originated, more than five years before current fiscal year	0	0
Revolving loans	0	0
Total	1	8
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