Segment Information (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
Segment Reporting Information [Line Items]
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
Insurance earned premiums and contract revenues									571	604	543
Investment and other income									173	113	236
Total gross revenues									7,988	8,146	8,843
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
Provision for credit losses	14	88	3	16	38	56	11	(203)	121	(98)	(433)
Operating and administrative expenses									911	857	1,059
Insurance losses and loss adjustment expenses									293	325	247
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
Total assets	95,302				88,913				95,302	88,913	91,704
Finance Operations [Member]
Segment Reporting Information [Line Items]
Total financing revenues									7,219	7,413	8,042
Insurance earned premiums and contract revenues									0	0	0
Investment and other income									57	44	46
Total gross revenues									7,276	7,457	8,088
Depreciation on operating leases									3,568	3,339	3,353
Interest expense									940	1,303	1,620
Provision for credit losses									121	(98)	(433)
Operating and administrative expenses									734	703	903
Insurance losses and loss adjustment expenses									0	0	0
Provision for income taxes									730	860	1,014
Net income									1,183	1,350	1,631
Total assets	92,504				86,049				92,504	86,049	89,141
Insurance Operations [Member]
Segment Reporting Information [Line Items]
Total financing revenues									0	0	0
Insurance earned premiums and contract revenues									596	620	565
Investment and other income									116	72	196
Total gross revenues									712	692	761
Depreciation on operating leases									0	0	0
Interest expense									0	0	0
Provision for credit losses									0	0	0
Operating and administrative expenses									177	154	156
Insurance losses and loss adjustment expenses									293	325	247
Provision for income taxes									94	77	136
Net income									148	136	222
Total assets	3,502				3,233				3,502	3,233	3,094
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues									25	16	22
Insurance earned premiums and contract revenues									(25)	(16)	(22)
Investment and other income									0	(3)	(6)
Total gross revenues									0	(3)	(6)
Depreciation on operating leases									0	0	0
Interest expense									0	(3)	(6)
Provision for credit losses									0	0	0
Operating and administrative expenses									0	0	0
Insurance losses and loss adjustment expenses									0	0	0
Provision for income taxes									0	0	0
Net income									0	0	0
Total assets	$ (704)				$ (369)				$ (704)	$ (369)	$ (531)