Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2012
Net financing revenues:
Manufacturer's subvention support and other revenues	$ 226	$ 243
Credit support fees incurred	(8)	(8)
Foreign exchange gain (loss) on notes receivable to affiliates	0	0
Foreign exchange gain (loss) on loans payable to affiliates	(39)	(38)
Interest expense on loans payable to affiliates	(3)	(11)
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	49	54
Investments and other income, net:
Interest earned on notes receivable from affiliates	1	0
Expenses:
Shared services charges and other expenses	16	17
Employee benefits expense	7	10
Investment in marketable securities
Investments in marketable securities	0		0
Finance receivables, net
Accounts receivable from affiliates	17		17
Direct finance receivables from affiliates	4		4
Notes receivable under home loan programs	19		19
Deferred retail subvention income from affiliates	(612)		(598)
Investments in operating leases, net
Leases to affiliates	4		4
Deferred lease subvention income from affiliates	(594)		(592)
Other assets
Notes receivable from alliliates	612		1,052
Other receivables from affiliates	12		8
Subvention support receivable from affiliates	101		65
Debt:
Loans payable to affiliate	0		2,201
Other liabilities
Unearned affiliates insurance premiums and contract revenues	255		273
Accounts payable to affiliates	32		58
Notes payable to affiliate	47		61
Shareholder's Equity:
Dividends paid	0		741
Stock based compensation	$ 2		$ 2