Variable Interest Entities - Schedule of Assets and Liabilities related to Variable Interest Entities Securitization Transactions (Details) - USD ($) $ in Millions	Jun. 30, 2018	Mar. 31, 2018
Variable Interest Entity [Line Items]
Restricted Cash	$ 1,048	$ 1,219
Net Securitized Assets	70,466	69,647
Other Assets	1,617	1,614
Debt	100,589	98,353
Other liabilities	4,306	3,987
Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	1,028	1,026
Gross Securitized Assets	22,349	19,999
Net Securitized Assets	19,286	17,633
Other Assets	126	125
Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	14,556	13,638
Other liabilities	10	10
Retail Finance Receivables [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	662	729
Gross Securitized Assets	11,776	12,130
Net Securitized Assets	11,573	11,927
Other Assets	5	7
Retail Finance Receivables [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	9,631	9,958
Other liabilities	8	7
Investments In Operating Leases, Net [Member] | Other assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	366	297
Gross Securitized Assets	10,573	7,869
Net Securitized Assets	7,713	5,706
Other Assets	121	118
Investments In Operating Leases, Net [Member] | Other liabilities [Member]
Variable Interest Entity [Line Items]
Debt	4,925	3,680
Other liabilities	$ 2	$ 3