Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,999	$ 2,912
Depreciation on operating leases	1,441	1,685
Interest expense	286	548
Net financing revenues	1,272	679
Voluntary protection contract revenues and insurance earned premiums	249	235
Investment and other income, net	156	176
Net financing revenues and other revenues	1,677	1,090
Expenses:
Provision for credit losses	(3)	183
Operating and administrative expenses	384	345
Voluntary protection contract expenses and insurance losses	108	75
Total expenses	489	603
Income before income taxes	1,188	487
Provision for income taxes	267	113
Net income	921	374
Total assets	134,401	134,743	$ 133,728
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, net	0	0
Net financing revenues and other revenues	0	0
Expenses:
Provision for credit losses	0	0
Operating and administrative expenses	0	0
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	0	0
Income before income taxes	0	0
Provision for income taxes	0	0
Net income	0	0
Total assets	(138)	(42)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,999	2,912
Depreciation on operating leases	1,441	1,685
Interest expense	286	548
Net financing revenues	1,272	679
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income, net	19	32
Net financing revenues and other revenues	1,291	711
Expenses:
Provision for credit losses	(3)	183
Operating and administrative expenses	292	256
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	289	439
Income before income taxes	1,002	272
Provision for income taxes	221	62
Net income	781	210
Total assets	128,015	129,065
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	249	235
Investment and other income, net	137	144
Net financing revenues and other revenues	386	379
Expenses:
Provision for credit losses	0	0
Operating and administrative expenses	92	89
Voluntary protection contract expenses and insurance losses	108	75
Total expenses	200	164
Income before income taxes	186	215
Provision for income taxes	46	51
Net income	140	164
Total assets	$ 6,524	$ 5,720