Guarantor Condensed Consolidating Financial Statements - Guarantor Income Statements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Income Statements, Captions [Line Items]
Finance charge income	$ 862	$ 818
Leased vehicle income	1,942	1,184
Other income	75	73
Total revenue	2,879	2,075
Salaries and benefits	229	193
Other operating expenses	163	141
Total operating expenses	392	334
Leased vehicle expenses	1,438	893
Provision for loan losses	217	196
Interest expense	619	463
Total costs and expenses	2,666	1,886
Equity income	47	36
Income before income taxes	260	225
Income tax (benefit) provision	58	61
Net income	202	164
Comprehensive income	292	316
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0
Leased vehicle income	0	0
Other income	0	(1)
Total revenue	0	(1)
Salaries and benefits	0	0
Other operating expenses	7	(4)
Total operating expenses	7	(4)
Leased vehicle expenses	0	0
Provision for loan losses	0	0
Interest expense	235	176
Total costs and expenses	242	172
Equity income	315	255
Income before income taxes	73	82
Income tax (benefit) provision	(129)	(82)
Net income	202	164
Comprehensive income	292	316
Guarantor [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	95	99
Leased vehicle income	0	0
Other income	273	205
Total revenue	368	304
Salaries and benefits	163	135
Other operating expenses	44	68
Total operating expenses	207	203
Leased vehicle expenses	0	0
Provision for loan losses	73	103
Interest expense	33	(30)
Total costs and expenses	313	276
Equity income	215	168
Income before income taxes	270	196
Income tax (benefit) provision	26	12
Net income	244	184
Comprehensive income	248	223
Non-Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	767	719
Leased vehicle income	1,942	1,184
Other income	1	15
Total revenue	2,710	1,918
Salaries and benefits	66	58
Other operating expenses	222	170
Total operating expenses	288	228
Leased vehicle expenses	1,438	893
Provision for loan losses	144	93
Interest expense	440	370
Total costs and expenses	2,310	1,584
Equity income	47	36
Income before income taxes	447	370
Income tax (benefit) provision	161	131
Net income	286	239
Comprehensive income	386	398
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Finance charge income	0	0
Leased vehicle income	0	0
Other income	(199)	(146)
Total revenue	(199)	(146)
Salaries and benefits	0	0
Other operating expenses	(110)	(93)
Total operating expenses	(110)	(93)
Leased vehicle expenses	0	0
Provision for loan losses	0	0
Interest expense	(89)	(53)
Total costs and expenses	(199)	(146)
Equity income	(530)	(423)
Income before income taxes	(530)	(423)
Income tax (benefit) provision	0	0
Net income	(530)	(423)
Comprehensive income	$ (634)	$ (621)