Segment Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Segment Reporting Information [Line Items]
Total financing revenues	$ 7,429	$ 8,064	$ 8,163
Insurance earned premiums and contract revenues	604	543	452
Investment and other income	113	236	228
Depreciation on operating leases	3,339	3,353	3,564
Interest expense	1,300	1,614	2,023
Provision for credit losses	(98)	(433)	604
Operating and administrative expenses	857	1,059	760
Insurance losses and loss adjustment expenses	325	247	213
Provision for income taxes	937	1,150	616
Net income	1,486	1,853	1,063
Total assets	$ 88,913	$ 91,704