Condensed Consolidated Statement of Comprehensive Income Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Revenue and Other Income [Line Items]
Interest and fees on finance receivables and loans	$ 1,860	$ 1,647	$ 3,667	$ 3,190
Interest on loans held-for-sale	3	6	5	6
Interest and Dividends on investment securities	244	188	484	364
Interest on cash and cash equivalents	21	17	44	32
Operating Lease, Lease Income	363	374	724	756
Total financing revenue and other interest income	2,491	2,232	4,924	4,348
Interest Expense [Abstract]
Interest on deposits	651	399	1,243	750
Interest on short-term borrowings	37	40	81	72
Interest on long-term debt	407	434	826	845
Total interest expense	1,095	873	2,150	1,667
Net depreciation expense on operating lease assets	239	265	485	538
Net financing revenue and other interest income	1,157	1,094	2,289	2,143
Other revenue [Abstract]
Insurance premiums and service revenue earned	261	239	522	495
Gain on mortgage and automotive loans, net	2	1	12	2
Other gain (loss) on investments, net	39	27	147	15
Other income, net of losses	93	97	180	206
Total other revenue	395	364	861	718
Total net revenue	1,552	1,458	3,150	2,861
Provision for loan losses	177	158	459	419
Noninterest Expense [Abstract]
Compensation and benefits expense	296	292	614	598
Insurance losses and loss adjustment expenses	127	101	186	164
Other operating expenses	458	446	911	891
Total noninterest expense	881	839	1,711	1,653
Income from continuing operations before income tax (benefit) expense	494	461	980	789
Statement [Abstract]
Income tax expense from continuing operations	(90)	113	21	189
Net income from continuing operations	584	348	959	600
(Loss) income from discontinued operations, net of tax	(2)	1	(3)	(1)
Net income	582	349	956	599
Other Comprehensive Income (Loss), Net of Tax	309	(70)	615	(398)
Comprehensive income	$ 891	$ 279	$ 1,571	$ 201
Earnings Per Share, Basic [Abstract]
Net income from continuing operations, basic earnings per common share	$ 1.47	$ 0.81	$ 2.39	$ 1.38
Loss from discontinued operations, net of tax, basic earnings per common share	0	0	(0.01)	0
Net income, basic earnings per common share	1.46	0.81	2.39	1.38
Earnings Per Share, Diluted [Abstract]
Net income from continuing operations, diluted earnings per common share	1.46	0.80	2.38	1.38
Loss from discontinued operations, net of tax, diluted earnings per common share	0	0	(0.01)	0
Net income, diluted earnings per common share	1.46	0.81	2.37	1.37
Cash dividends declared per common share	$ 0.17	$ 0.13	$ 0.34	$ 0.26