Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Selected Quarterly Financial Data (Unaudited) [Abstract]
Total financing revenues	$ 1,821	$ 1,815	$ 1,811	$ 1,797	$ 1,804	$ 1,835	$ 1,870	$ 1,920	$ 7,244	$ 7,429	$ 8,064
Depreciation on operating leases	932	901	880	855	841	844	829	825	3,568	3,339	3,353
Interest expense	315	284	283	58	531	163	149	457	940	1,300	1,614
Net financing revenues	574	630	648	884	432	828	892	638	2,736	2,790	3,097
Other income	173	203	183	185	171	212	144	190
Provision for credit losses	14	88	3	16	38	56	11	(203)	121	(98)	(433)
Expenses	299	306	302	297	318	286	295	283
Income before income taxes	434	439	526	756	247	698	730	748	2,155	2,423	3,003
Provision for income taxes	189	156	200	279	109	266	279	283	824	937	1,150
Net income	$ 245	$ 283	$ 326	$ 477	$ 138	$ 432	$ 451	$ 465	$ 1,331	$ 1,486	$ 1,853