Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019
Variable Interest Entity [Line Items]
Restricted cash	$ 1,739	$ 985
Net securitized assets	73,996	70,517
Other assets	2,823	1,981
Debt	97,740	92,922
Other liabilities	7,854	4,564
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	996	985
Net securitized assets	17,961	16,382
Other assets	131	192
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	14,568	12,401
Other liabilities	12	12
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	694	630
Net securitized assets	12,375	11,075
Other assets	5	6
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	10,933	9,202
Other liabilities	10	10
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted cash	302	355
Net securitized assets	5,586	5,307
Other assets	126	186
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	3,635	3,199
Other liabilities	$ 2	$ 2