Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018
Variable Interest Entity [Line Items]
Restricted Cash	$ 985	$ 1,219
Net Securitized Assets	70,517	69,647
Other Assets	1,981	1,614
Debt	92,922	98,353
Other liabilities	4,564	3,987
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	985	1,026
Gross Securitized Assets	18,850	19,999
Net Securitized Assets	16,382	17,633
Other Assets	192	125
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	12,401	13,638
Other liabilities	12	10
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	630	729
Gross Securitized Assets	11,318	12,130
Net Securitized Assets	11,075	11,927
Other Assets	6	7
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	9,202	9,958
Other liabilities	10	7
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	355	297
Gross Securitized Assets	7,532	7,869
Net Securitized Assets	5,307	5,706
Other Assets	186	118
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	3,199	3,680
Other liabilities	$ 2	$ 3