Allowance for Credit Losses - Allowance for Credit Losses and Finance Receivables by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Jun. 30, 2024		Jun. 30, 2023		Mar. 31, 2024
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs	$ 0				$ 0
Provision for credit losses	189		$ 165
Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs	(198)				(776)
Finance Receivables, Net [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,684		1,513		1,513
Charge-offs	(198)		(134)
Recoveries	30		29
Provision for credit losses	189		165
Allowance for credit losses at end of period	1,705	[1]	1,573	[2]	1,684
Finance Receivables, Net [Member] | Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,549		1,430		1,430
Charge-offs	(198)		(134)
Recoveries	30		29
Provision for credit losses	178		158
Allowance for credit losses at end of period	1,559	[1]	1,483	[2]	1,549
Finance Receivables, Net [Member] | Dealer products [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	135		83		83
Charge-offs	0		0
Recoveries	0		0
Provision for credit losses	11		7
Allowance for credit losses at end of period	$ 146	[1]	$ 90	[2]	$ 135

[1] Ending balance includes $52 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 $28 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.