Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Variable Interest Entity [Line Items]
Restricted Cash	$ 1,219	$ 1,087
Net Securitized Assets	69,647	68,462
Other Assets	1,614	2,044
Debt	98,353	98,233
Other liabilities	3,987	3,952
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	1,026	1,067
Gross Securitized Assets	19,999	19,573
Net Securitized Assets	17,633	17,753
Other Assets	125	87
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	13,638	14,319
Other liabilities	10	6
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	729	856
Gross Securitized Assets	12,130	13,071
Net Securitized Assets	11,927	12,865
Other Assets	7	7
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	9,958	11,017
Other liabilities	7	5
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	297	211
Gross Securitized Assets	7,869	6,502
Net Securitized Assets	5,706	4,888
Other Assets	118	80
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	3,680	3,302
Other liabilities	$ 3	$ 1