Condensed Consolidated Statement of Comprehensive Income Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Revenue and Other Income [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,647	$ 1,447	$ 3,190	$ 2,815
Interest and Fee Income, Loans and Leases Held-for-sale	6	0	6	0
Interest and Dividend Income, Securities, Operating, Available-for-sale	188	146	364	280
Interest Income, Deposits with Financial Institutions	17	7	32	12
Operating Leases, Income Statement, Lease Revenue	374	488	756	1,031
Total financing revenue and other interest income	2,232	2,088	4,348	4,138
Interest Expense [Abstract]
Interest Expense, Deposits	399	250	750	481
Interest Expense, Short-term Borrowings	40	33	72	60
Interest Expense, Long-term Debt	434	417	845	841
Interest Expense	873	700	1,667	1,382
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	265	321	538	710
Net Financing Revenue	1,094	1,067	2,143	2,046
Other revenue [Abstract]
Insurance Services Revenue	239	227	495	468
Gain (Loss) on Sales of Loans, Net	1	36	2	50
Gain (Loss) on Investments	27	23	15	50
Noninterest Income, Other Operating Income	97	102	206	216
Nonoperating Income (Expense)	364	388	718	784
Revenues	1,458	1,455	2,861	2,830
Provision for Loan Losses Expensed	158	269	419	540
Noninterest Expense [Abstract]
Labor and Related Expense	292	265	598	550
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	101	125	164	213
Other Noninterest Expense	446	420	891	825
Noninterest Expense	839	810	1,653	1,588
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	461	376	789	702
Income Tax Expense (Benefit)	113	122	189	235
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	348	254	600	467
Net Income (Loss) Attributable to Parent	349	252	599	466
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(70)	76	(398)	96
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	279	328	201	562
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ 1	$ (2)	$ (1)	$ (1)
Earnings Per Share, Basic [Abstract]
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.81	$ 0.55	$ 1.38	$ 1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	(0.01)	0.00	0.00
Earnings Per Share, Basic	0.81	0.55	1.38	1.01
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	0.80	0.55	1.38	1.01
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	(0.01)	0.00	0.00
Earnings Per Share, Diluted	0.81	0.55	1.37	1.01
Common Stock, Dividends, Per Share, Declared	$ 0.13	$ 0.08	$ 0.26	$ 0.16
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	$ 349	$ 252	$ 599	$ 466