Allowance for Credit Losses - Allowance for Credit Losses and Finance Receivables by Portfolio Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2024		Mar. 31, 2023		Mar. 31, 2022
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs	$ 0
Provision for credit losses	839		$ 713		$ 236
Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs	(776)
Finance Receivables, Net [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,513	[1]	1,272
Charge-offs	(776)		(535)
Recoveries	108		63
Provision for credit losses	839		713
Allowance for credit losses at end of period	1,684	[2]	1,513	[1]	1,272
Finance Receivables, Net [Member] | Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,430	[1]	1,195
Charge-offs	(776)		(535)
Recoveries	108		63
Provision for credit losses	787		707
Allowance for credit losses at end of period	1,549	[2]	1,430	[1]	1,195
Finance Receivables, Net [Member] | Dealer products [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	83	[1]	77
Charge-offs	0		0
Recoveries	0		0
Provision for credit losses	52		6
Allowance for credit losses at end of period	$ 135	[1]	$ 83	[1]	$ 77

[1] Ending balance includes $24 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 $47 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.