Variable Interest Entities - Schedule of Variable Interest Entities, Securitization Transactions Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Mar. 31, 2015
Variable Interest Entity [Line Items]
Restricted Cash	$ 853	$ 784
Net Securitized Assets	65,763	65,893
Other assets	2,303	2,282
Debt	94,708	90,231
Other liabilities	3,722	3,355
Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	852	784
Gross Securitized Assets	17,451	13,253
Net Securitized Assets	16,408	12,702
Other assets	55	15
Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	14,030	10,837
Other liabilities	4	3
Retail Finance Receivables [Member] | Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	741	730
Gross Securitized Assets	13,794	11,682
Net Securitized Assets	13,611	11,509
Other assets	7	4
Retail Finance Receivables [Member] | Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	12,068	9,980
Other liabilities	3	3
Investments In Operating Leases, Net [Member] | Variable Interest Entities Securitized Assets [Member]
Variable Interest Entity [Line Items]
Restricted Cash	111	54
Gross Securitized Assets	3,657	1,571
Net Securitized Assets	2,797	1,193
Other assets	48	11
Investments In Operating Leases, Net [Member] | Related Liabilities [Member]
Variable Interest Entity [Line Items]
Debt	1,962	857
Other liabilities	$ 1	$ 0