Condensed Consolidated Statement of Comprehensive Income Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Revenue and Other Income [Line Items]
Interest and fees on finance receivables and loans	$ 1,807	$ 1,543
Interest on loans held-for-sale	2	0
Interest and dividends on investment securities and other earning assets	240	176
Interest on cash and cash equivalents	23	15
Operating leases	361	382
Total financing revenue and other interest income	2,433	2,116
Interest Expense [Abstract]
Interest on deposits	592	351
Interest on short-term borrowings	44	32
Interest on long-term debt	419	411
Total interest expense	1,055	794
Net depreciation expense on operating lease assets	246	273
Net financing revenue and other interest income	1,132	1,049
Other revenue [Abstract]
Insurance premiums and service revenue earned	261	256
Gain on mortgage and automotive loans, net	10	1
Other (loss) gain on investments, net	108	(12)
Other income, net of losses	87	109
Total other revenue	466	354
Total net revenue	1,598	1,403
Provision for loan losses	282	261
Noninterest Expense [Abstract]
Compensation and benefits expense	318	306
Insurance losses and loss adjustment expenses	59	63
Other operating expenses	453	445
Total noninterest expense	830	814
Income from continuing operations before income tax expense	486	328
Income tax expense from continuing operations	111	76
Net income from continuing operations	375	252
Net income	374	250
Other comprehensive income (loss), net of tax	306	(328)
Comprehensive income	680	(78)
Income (loss) from discontinued operations, net of tax	$ (1)	$ (2)
Earnings Per Share, Basic [Abstract]
Net income from continuing operations, basic earnings per common share	$ 0.93	$ 0.58
Income (loss) from discontinued operations, net of tax, basic earnings per common share	0.00	(0.01)
Net income, basic earnings per common share	0.93	0.57
Earnings Per Share, Diluted [Abstract]
Net income from continuing operations, diluted earnings per common share	0.92	0.57
Income (loss) from discontinued operations, net of tax, diluted earnings per common share	0.00	(0.01)
Net income, diluted earnings per common share	0.92	0.57
Cash dividends declared per common share	$ 0.17	$ 0.13
Retained earnings
Net income	$ 374	$ 250