Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Mar. 31, 2013
Net financing revenues:
Manufacturer's subvention support and other revenues	$ 232	$ 226
Credit support fees incurred	(20)	(8)
Foreign exchange gain (loss) on notes receivable to affiliates	0	0
Foreign exchange gain (loss) on loans payable to affiliates	0	(39)
Interest expense on loans payable to affiliates	0	(3)
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	33	49
Investments and other income, net:
Interest earned on notes receivable from affiliates	1	1
Expenses:
Shared services charges and other expenses	14	16
Employee benefits expense	9	7
Investment in marketable securities
Investments in affiliates commercial paper	24		2
Finance receivables, net
Accounts receivable from affiliates	71		22
Direct finance receivables from affiliates	6		6
Notes receivable under home loan programs	17		18
Deferred retail subvention income from affiliates	(725)		(699)
Investments in operating leases, net
Leases to affiliates	7		7
Deferred lease subvention income from affiliates	(647)		(604)
Other assets
Notes receivable from alliliates	1,250		931
Other receivables from affiliates	1		1
Subvention support receivable from affiliates	129		88
Debt:
Loans payable to affiliate	0		0
Other liabilities
Unearned affiliates insurance premiums and contract revenues	241		235
Accounts payable to affiliates	153		192
Notes payable to affiliate	48		48
Shareholder's Equity:
Dividends paid	0		1,487
Stock based compensation	$ 2		$ 2