Guarantor Condensed Consolidating Financial Statements Guarantor Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Condensed Income Statements, Captions [Line Items]
Finance charge income	$ 848	$ 882	$ 1,702	$ 1,712
Leased vehicle income	599	238	1,030	438
Other income	68	71	137	138
Total revenue	1,515	1,191	2,869	2,288
Salaries and benefits	181	154	346	290
Other operating expenses	138	126	279	259
Total operating expenses	319	280	625	549
Leased vehicle expenses	467	179	794	335
Provision for loan losses	141	113	296	248
Interest expense	391	354	771	669
Total costs and expenses	1,318	926	2,486	1,801
Equity income	28	0	56	0
Income before income taxes	225	265	439	487
Income tax (benefit) provision	39	90	103	167
Net income	186	175	336	320
Comprehensive income	291	224	95	374
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0	0	0
Leased vehicle income	0	0	0	0
Other income	4	20	11	40
Total revenue	4	20	11	40
Salaries and benefits	0	0	0	0
Other operating expenses	(19)	(6)	35	(5)
Total operating expenses	(19)	(6)	35	(5)
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	114	44	208	99
Total costs and expenses	95	38	243	94
Equity income	223	189	461	359
Income before income taxes	132	171	229	305
Income tax (benefit) provision	(54)	(4)	(107)	(15)
Net income	186	175	336	320
Comprehensive income	291	224	95	374
Guarantor [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	100	39	180	69
Leased vehicle income	0	0	0	0
Other income	118	104	226	231
Total revenue	218	143	406	300
Salaries and benefits	77	63	166	116
Other operating expenses	73	41	70	74
Total operating expenses	150	104	236	190
Leased vehicle expenses	0	0	0	0
Provision for loan losses	116	75	190	135
Interest expense	3	8	1	19
Total costs and expenses	269	187	427	344
Equity income	156	153	285	269
Income before income taxes	105	109	264	225
Income tax (benefit) provision	(20)	(16)	(9)	(16)
Net income	125	125	273	241
Comprehensive income	139	148	229	244
Non-Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	748	843	1,522	1,643
Leased vehicle income	599	238	1,030	438
Other income	40	42	85	80
Total revenue	1,387	1,123	2,637	2,161
Salaries and benefits	104	91	180	174
Other operating expenses	149	153	303	314
Total operating expenses	253	244	483	488
Leased vehicle expenses	467	179	794	335
Provision for loan losses	25	38	106	113
Interest expense	303	335	618	640
Total costs and expenses	1,048	796	2,001	1,576
Equity income	28	0	56	0
Income before income taxes	367	327	692	585
Income tax (benefit) provision	113	110	219	198
Net income	254	217	473	387
Comprehensive income	353	267	228	442
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0	0	0
Leased vehicle income	0	0	0	0
Other income	(94)	(95)	(185)	(213)
Total revenue	(94)	(95)	(185)	(213)
Salaries and benefits	0	0	0	0
Other operating expenses	(65)	(62)	(129)	(124)
Total operating expenses	(65)	(62)	(129)	(124)
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	(29)	(33)	(56)	(89)
Total costs and expenses	(94)	(95)	(185)	(213)
Equity income	(379)	(342)	(746)	(628)
Income before income taxes	(379)	(342)	(746)	(628)
Income tax (benefit) provision	0	0	0	0
Net income	(379)	(342)	(746)	(628)
Comprehensive income	$ (492)	$ (415)	$ (457)	$ (686)