Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Dec. 31, 2019	Mar. 31, 2019
Variable Interest Entity [Line Items]
Restricted Cash	$ 940	$ 985
Net Securitized Assets	73,450	70,517
Other Assets	2,355	1,981
Debt	97,534	92,922
Other liabilities	4,828	4,564
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	940	985
Net Securitized Assets	16,600	16,382
Other Assets	121	192
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	13,344	12,401
Other liabilities	12	12
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	690	630
Net Securitized Assets	12,352	11,075
Other Assets	4	6
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	10,698	9,202
Other liabilities	10	10
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	250	355
Net Securitized Assets	4,248	5,307
Other Assets	117	186
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	2,646	3,199
Other liabilities	$ 2	$ 2