Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Variable Interest Entity [Line Items]
Restricted cash	$ 1,957	$ 1,739
Net securitized assets	79,192	73,996
Other assets	2,473	2,823
Debt	109,725	97,740
Other liabilities	5,548	7,854
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	1,957	996
Net securitized assets	28,344	17,961
Other assets	89	131
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	24,212	14,568
Other liabilities	14	12
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	1,521	694
Net securitized assets	21,745	12,375
Other assets	46	5
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	19,665	10,933
Other liabilities	13	10
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	436	302
Net securitized assets	6,599	5,586
Other assets	43	126
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	4,547	3,635
Other liabilities	$ 1	$ 2