Guarantor Condensed Consolidating Financial Statements - Guarantor Income Statements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Income Statements, Captions [Line Items]
Finance charge income	$ 837	$ 842	$ 2,481	$ 2,544
Leased vehicle income	1,590	797	4,164	1,827
Other income	72	68	221	205
Total revenue	2,499	1,707	6,866	4,576
Salaries and benefits	223	185	619	531
Other operating expenses	169	135	450	414
Total operating expenses	392	320	1,069	945
Leased vehicle expenses	1,202	629	3,163	1,423
Provision for loan losses	172	144	519	440
Interest expense	541	412	1,505	1,183
Total costs and expenses	2,307	1,505	6,256	3,991
Equity income	36	29	109	85
Income before income taxes	228	231	719	670
Income tax (benefit) provision	81	52	219	155
Net income	147	179	500	515
Comprehensive income (loss)	136	(103)	555	(8)
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	2	(1)	13
Total revenue	0	2	(1)	13
Salaries and benefits	0	0	0	0
Other operating expenses	6	21	2	56
Total operating expenses	6	21	2	56
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	171	134	612	342
Total costs and expenses	177	155	614	398
Equity income	267	255	858	716
Income before income taxes	90	102	243	331
Income tax (benefit) provision	(57)	(77)	(257)	(184)
Net income	147	179	500	515
Comprehensive income (loss)	136	(103)	555	(8)
Guarantor [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	127	114	344	294
Leased vehicle income	0	0	0	0
Other income	213	137	628	363
Total revenue	340	251	972	657
Salaries and benefits	157	79	432	245
Other operating expenses	54	25	175	95
Total operating expenses	211	104	607	340
Leased vehicle expenses	0	0	0	0
Provision for loan losses	102	112	282	302
Interest expense	54	0	(67)	1
Total costs and expenses	367	216	822	643
Equity income	202	167	538	452
Income before income taxes	175	202	688	466
Income tax (benefit) provision	(17)	15	63	6
Net income	192	187	625	460
Comprehensive income (loss)	183	141	653	370
Non-Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	710	728	2,137	2,250
Leased vehicle income	1,590	797	4,164	1,827
Other income	30	33	74	118
Total revenue	2,330	1,558	6,375	4,195
Salaries and benefits	66	106	187	286
Other operating expenses	210	150	565	453
Total operating expenses	276	256	752	739
Leased vehicle expenses	1,202	629	3,163	1,423
Provision for loan losses	70	32	237	138
Interest expense	386	321	1,148	939
Total costs and expenses	1,934	1,238	5,300	3,239
Equity income	36	29	109	85
Income before income taxes	432	349	1,184	1,041
Income tax (benefit) provision	155	114	413	333
Net income	277	235	771	708
Comprehensive income (loss)	270	(47)	837	181
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0	0	0
Leased vehicle income	0	0	0	0
Other income	(171)	(104)	(480)	(289)
Total revenue	(171)	(104)	(480)	(289)
Salaries and benefits	0	0	0	0
Other operating expenses	(101)	(61)	(292)	(190)
Total operating expenses	(101)	(61)	(292)	(190)
Leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	(70)	(43)	(188)	(99)
Total costs and expenses	(171)	(104)	(480)	(289)
Equity income	(469)	(422)	(1,396)	(1,168)
Income before income taxes	(469)	(422)	(1,396)	(1,168)
Income tax (benefit) provision	0	0	0	0
Net income	(469)	(422)	(1,396)	(1,168)
Comprehensive income (loss)	$ (453)	$ (94)	$ (1,490)	$ (551)