Variable Interest Entities - Schedule of Variable Interest Entities, Securitization Transactions Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015
Variable Interest Entity [Line Items]
Restricted Cash	$ 1,583	$ 784
Net Securitized Assets	66,396	65,893
Other assets	1,655	2,282
Debt	91,677	90,231
Other Liabilities	3,446	3,355
Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	811	784
Gross Securitized Assets	14,580	13,253
Net Securitized Assets	14,030	12,702
Other assets	22	15
Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	11,996	10,837
Other Liabilities	2	3
Retail Finance Receivables [Member] | Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	764	730
Gross Securitized Assets	13,165	11,682
Net Securitized Assets	12,978	11,509
Other assets	4	4
Retail Finance Receivables [Member] | Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	11,268	9,980
Other Liabilities	2	3
Investments In Operating Leases, Net [Member] | Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	47	54
Gross Securitized Assets	1,415	1,571
Net Securitized Assets	1,052	1,193
Other assets	18	11
Investments In Operating Leases, Net [Member] | Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	728	857
Other Liabilities	$ 0	$ 0