Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019
Variable Interest Entity [Line Items]
Restricted Cash	$ 1,008	$ 985
Net Securitized Assets	72,052	70,517
Other Assets	2,036	1,981
Debt	97,384	92,922
Other liabilities	4,711	4,564
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	1,008	985
Gross Securitized Assets	18,854	18,850
Net Securitized Assets	16,789	16,382
Other Assets	110	192
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	12,916	12,401
Other liabilities	13	12
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	709	630
Gross Securitized Assets	12,950	11,318
Net Securitized Assets	12,677	11,075
Other Assets	6	6
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	10,616	9,202
Other liabilities	11	10
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	299	355
Gross Securitized Assets	5,904	7,532
Net Securitized Assets	4,112	5,307
Other Assets	104	186
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	2,300	3,199
Other liabilities	$ 2	$ 2