Allowance for Credit Losses - Allowance for Credit Losses and Finance Receivables by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable Allowance For Credit Losses [Abstract]
Provision for credit losses			$ 110	$ 366
Finance Receivables, Net [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	$ 1,224	$ 1,174	1,215	727
Charge-offs	(64)	(113)	(152)	(228)
Recoveries	14	20	46	42
Provision for credit losses	45	118	110	366
Allowance for credit losses at end of period	1,219	1,199	1,219	1,199
Finance Receivables, Net [Member] | ASU 2016-13 [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Adoption of ASU 2016-13	0			292
Finance Receivables, Net [Member] | Retail loan [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	1,135	1,020	1,075	486
Charge-offs	(64)	(113)	(152)	(228)
Recoveries	14	12	46	33
Provision for credit losses	55	133	171	480
Allowance for credit losses at end of period	1,140	1,052	1,140	1,052
Finance Receivables, Net [Member] | Retail loan [Member] | ASU 2016-13 [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Adoption of ASU 2016-13	0			281
Finance Receivables, Net [Member] | Dealer products [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Allowance for credit losses at beginning of period	89	154	140	241
Charge-offs	0	0	0	0
Recoveries	0	8	0	9
Provision for credit losses	(10)	(15)	(61)	(114)
Allowance for credit losses at end of period	79	$ 147	$ 79	147
Finance Receivables, Net [Member] | Dealer products [Member] | ASU 2016-13 [Member]
Financing Receivable Allowance For Credit Losses [Abstract]
Adoption of ASU 2016-13	$ 0			$ 11