Guarantor Condensed Consolidating Financial Statements Guarantor Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Income Statements, Captions [Line Items]
Finance charge income	$ 826	$ 848	$ 1,644	$ 1,702
Leased vehicle income	1,390	599	2,574	1,030
Other income	76	68	149	137
Total revenue	2,292	1,515	4,367	2,869
Salaries and benefits	203	181	396	346
Other operating expenses	140	138	281	279
Total operating expenses	343	319	677	625
Leased vehicle expenses	1,068	467	1,961	794
Provision for loan losses	151	141	347	296
Interest expense	501	391	964	771
Total costs and expenses	2,063	1,318	3,949	2,486
Equity income	37	28	73	56
Income before income taxes	266	225	491	439
Income tax (benefit) provision	77	39	138	103
Net income	189	186	353	336
Comprehensive income	103	291	419	95
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	0	4	(1)	11
Total revenue	0	4	(1)	11
Salaries and benefits	0	0	0	0
Other operating expenses	0	(19)	(4)	35
Total operating expenses	0	(19)	(4)	35
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	265	114	441	208
Total costs and expenses	265	95	437	243
Equity income	336	223	591	461
Income before income taxes	71	132	153	229
Income tax (benefit) provision	(118)	(54)	(200)	(107)
Net income	189	186	353	336
Comprehensive income	103	291	419	95
Guarantor [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	118	100	217	180
Leased vehicle income	0	0	0	0
Other income	210	118	415	226
Total revenue	328	218	632	406
Salaries and benefits	140	77	275	166
Other operating expenses	53	73	121	70
Total operating expenses	193	150	396	236
Leased vehicle expenses	0	0	0	0
Provision for loan losses	77	116	180	190
Interest expense	(91)	3	(121)	1
Total costs and expenses	179	269	455	427
Equity income	168	156	336	285
Income before income taxes	317	105	513	264
Income tax (benefit) provision	68	(20)	80	(9)
Net income	249	125	433	273
Comprehensive income	247	139	470	229
Non-Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	708	748	1,427	1,522
Leased vehicle income	1,390	599	2,574	1,030
Other income	29	40	44	85
Total revenue	2,127	1,387	4,045	2,637
Salaries and benefits	63	104	121	180
Other operating expenses	185	149	355	303
Total operating expenses	248	253	476	483
Leased vehicle expenses	1,068	467	1,961	794
Provision for loan losses	74	25	167	106
Interest expense	392	303	762	618
Total costs and expenses	1,782	1,048	3,366	2,001
Equity income	37	28	73	56
Income before income taxes	382	367	752	692
Income tax (benefit) provision	127	113	258	219
Net income	255	254	494	473
Comprehensive income	169	353	567	228
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0	0	0
Leased vehicle income	0	0	0	0
Other income	(163)	(94)	(309)	(185)
Total revenue	(163)	(94)	(309)	(185)
Salaries and benefits	0	0	0	0
Other operating expenses	(98)	(65)	(191)	(129)
Total operating expenses	(98)	(65)	(191)	(129)
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	(65)	(29)	(118)	(56)
Total costs and expenses	(163)	(94)	(309)	(185)
Equity income	(504)	(379)	(927)	(746)
Income before income taxes	(504)	(379)	(927)	(746)
Income tax (benefit) provision	0	0	0	0
Net income	(504)	(379)	(927)	(746)
Comprehensive income	$ (416)	$ (492)	$ (1,037)	$ (457)