Income Taxes - Deferred Tax Liabilities and Assets (Details) - USD ($) $ in Millions		Mar. 31, 2023	Mar. 31, 2022
Liabilities:
Lease transactions		$ 4,786	$ 1,504
Voluntary protection dealer commissions		403	348
State taxes, net of federal tax benefit		356	275
Mark-to-market of investments in marketable securities and derivatives		0	24
Other		72	82
Deferred tax liabilities		5,617	2,233
Assets:
Net operating loss and tax credit carryforwards		1,007	14
Provision for credit and residual value losses		478	394
Deferred costs and fees		197	179
Mark-to-market of investments in marketable securities and derivatives		150	0
Accrued expenses		23	45
Lease obligations		20	23
Other		17	14
Deferred tax assets		1,892	669
Valuation allowance		(2)	0
Net deferred tax assets		1,890	669
Net deferred income tax liability	[1]	$ 3,727	$ 1,564

[1] Balance includes deferred tax assets of $16 million and $6 million at March 31, 2023 and 2022, respectively, attributable to unrealized losses included in accumulated other comprehensive loss. The change in this balance is not included in the total deferred tax expense.