Allowance for Credit Losses - Allowance for Credit Losses and Finance Receivables by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Sep. 30, 2023		Sep. 30, 2022		Sep. 30, 2023		Sep. 30, 2022
Financing Receivable Allowance For Credit Losses [Abstract]
Provision for credit losses					$ 386		$ 291
Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs					(325)
Finance Receivables, Net [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	$ 1,573		$ 1,274		1,513		1,272
Charge-offs	(191)		(106)		(325)		(197)
Recoveries	25		14		54		29
Provision for credit losses	221		213		386		291
Allowance for credit losses at end of period	1,628	[1]	1,395	[2]	1,628	[1]	1,395	[2]
Finance Receivables, Net [Member] | Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,483		1,209		1,430		1,195
Charge-offs	(191)		(106)		(325)		(197)
Recoveries	25		14		54		29
Provision for credit losses	212		204		370		294
Allowance for credit losses at end of period	1,529	[1]	1,321	[2]	1,529	[1]	1,321	[2]
Finance Receivables, Net [Member] | Dealer products [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	90		65		83		77
Charge-offs	0		0		0		0
Recoveries	0		0		0		0
Provision for credit losses	9		9		16		(3)
Allowance for credit losses at end of period	$ 99	[1]	$ 74	[2]	$ 99	[1]	$ 74	[2]

[1] Ending balance includes $33 million of allowance for credit losses recorded in Other liabilities on the Consolidated Balance Sheet which is related to off-balance sheet lending commitments in the dealer products portfolio.

[2] Ending balance includes $29 million of allowance for credit losses recorded in Other liabilities on the Consolidated Balance Sheet which is related to off-balance sheet lending commitments in the dealer products portfolio.