Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2023
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,904	$ 2,831
Depreciation on operating leases	1,157	1,409
Interest expense	899	563
Net financing revenues	848	859
Voluntary protection contract revenues and insurance earned premiums	271	259
Investment and other income (loss), net	162	(306)
Net financing revenues and other revenues	1,281	812
Expenses:
Provision for credit losses	165	78
Operating and administrative	448	406
Voluntary protection contract expenses and insurance losses	146	107
Total expenses	759	591
Income before income taxes	522	221
Provision (benefit) for income taxes	54	51
Net income	468	170
Total assets	138,732	136,132	$ 137,595
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0
Depreciation on operating leases	0	0
Interest expense	0	0
Net financing revenues	0	0
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income (loss), net	0	0
Net financing revenues and other revenues	0	0
Expenses:
Provision for credit losses	0	0
Operating and administrative	0	0
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	0	0
Income before income taxes	0	0
Provision (benefit) for income taxes	0	0
Net income	0	0
Total assets	(67)	(135)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,904	2,831
Depreciation on operating leases	1,157	1,409
Interest expense	899	563
Net financing revenues	848	859
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income (loss), net	114	33
Net financing revenues and other revenues	962	892
Expenses:
Provision for credit losses	165	78
Operating and administrative	334	299
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	499	377
Income before income taxes	463	515
Provision (benefit) for income taxes	41	125
Net income	422	390
Total assets	132,070	130,054
Voluntary Protection Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0
Depreciation on operating leases	0	0
Interest expense	0	0
Net financing revenues	0	0
Voluntary protection contract revenues and insurance earned premiums	271	259
Investment and other income (loss), net	48	(339)
Net financing revenues and other revenues	319	(80)
Expenses:
Provision for credit losses	0	0
Operating and administrative	114	107
Voluntary protection contract expenses and insurance losses	146	107
Total expenses	260	214
Income before income taxes	59	(294)
Provision (benefit) for income taxes	13	(74)
Net income	46	(220)
Total assets	$ 6,729	$ 6,213