Allowance for Credit Losses - Allowance for Credit Losses and Finance Receivables by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended				12 Months Ended
	Dec. 31, 2025		Dec. 31, 2024		Dec. 31, 2025		Dec. 31, 2024		Mar. 31, 2025
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs	$ 0				$ 0				$ 0
Provision for credit losses	152		$ 181		328		$ 576
Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Charge-offs					(628)				(887)
Finance Receivables, Net [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,572		1,709		1,704		1,684		1,684
Charge-offs	(235)		(231)		(628)		(666)
Recoveries	34		37		119		102
Provision for credit losses	152		181		328		576
Allowance for credit losses at end of period	1,523	[1]	1,696	[2]	1,523	[1]	1,696	[2]	1,704
Finance Receivables, Net [Member] | Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,387		1,563		1,544		1,549		1,549
Charge-offs	(235)		(231)		(628)		(666)
Recoveries	34		37		119		102
Provision for credit losses	164		199		315		583
Allowance for credit losses at end of period	1,350	[1]	1,568	[2]	1,350	[1]	1,568	[2]	1,544
Finance Receivables, Net [Member] | Dealer products [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	185		146		160		135		135
Charge-offs	0		0		0		0
Recoveries	0		0		0		0
Provision for credit losses	(12)		(18)		13		(7)
Allowance for credit losses at end of period	$ 173	[1]	$ 128	[2]	$ 173	[1]	$ 128	[2]	$ 160

[1] 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.

[2] Ending balance includes $50 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.