Parent and Guarantor Consolidating Financial Statements (Schedule of Condensed Consolidating Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									$ 5,819	$ 5,162	$ 4,570
Interest and Fee Income, Loans and Leases Held-for-sale									0	0	40
Interest and Dividend Income, Securities, Operating									599	418	381
Interest Income, Deposits with Financial Institutions									37	14	8
Operating Leases, Income Statement, Lease Revenue									1,867	2,711	3,398
Total financing revenue and other interest income									8,322	8,305	8,397
Interest Expense, Deposits									1,077	830	718
Interest Expense, Short-term Borrowings									127	57	49
Interest Expense, Long-term Debt									1,653	1,742	1,662
Interest Expense, Related Party									0	0	0
Interest Expense									2,857	2,629	2,429
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease									1,244	1,769	2,249
Net Financing Revenue	$ 1,094	$ 1,081	$ 1,067	$ 979	$ 976	$ 996	$ 984	$ 951	4,221	3,907	3,719
Dividends from Bank Subsidiary									0		0
Dividends From Non Bank Subsidiary									0	0	0
Insurance Services Revenue									973	945	940
Gain (Loss) on Sales of Loans, Net									68	11	45
Gain (Loss) on Extinguishment of Debt									(7)	(5)	(357)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									102	185	155
Noninterest Income, Other Operating Income									408	394	359
Nonoperating Income (Expense)	379	381	388	396	392	388	374	376	1,544	1,530	1,142
Revenues									5,765	5,437	4,861
Provision for Loan Losses Expensed	294	314	269	271	267	258	172	220	1,148	917	707
Labor and Related Expense									1,095	992	963
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims									332	342	293
Other Noninterest Expense									1,683	1,605	1,505
Noninterest Expense	769	753	810	778	721	735	773	710	3,110	2,939	2,761
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	410	395	376	326	380	391	413	397	1,507	1,581	1,393
Income Tax Expense (Benefit)	231	115	122	113	134	130	56	150	581	470	496
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	179	280	254	213	246	261	357	247	926	1,111	897
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	2	2	(2)	1	2	(52)	3	3	3	(44)	392
Undistributed income of bank subsidiaries									0	0	0
Undistributed income of nonbank subsidiaries									0	0	0
Net Income (Loss) Attributable to Parent	$ 181	$ 282	$ 252	$ 214	$ 248	$ 209	$ 360	$ 250	929	1,067	1,289
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									106	(110)	(165)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									1,035	957	1,124
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									(27)	(104)	(83)
Interest and Fee Income, Loans and Leases Held-for-sale											0
Interest and Dividend Income, Securities, Operating									0	0	0
Interest Income, Deposits with Financial Institutions									7	5	1
Operating Leases, Income Statement, Lease Revenue									11	17	9
Total financing revenue and other interest income									7	(71)	(56)
Interest Expense, Deposits									3	8	10
Interest Expense, Short-term Borrowings									60	40	40
Interest Expense, Long-term Debt									1,101	1,161	1,121
Interest Expense, Related Party									15	20	32
Interest Expense									1,179	1,229	1,203
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease									11	14	7
Net Financing Revenue									(1,183)	(1,314)	(1,266)
Dividends from Bank Subsidiary									3,300		525
Dividends From Non Bank Subsidiary									752	965	1,123
Insurance Services Revenue									0	0	0
Gain (Loss) on Sales of Loans, Net									40	(11)	(9)
Gain (Loss) on Extinguishment of Debt									(1)	(3)	(355)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									0	0	0
Noninterest Income, Other Operating Income									676	1,253	1,373
Nonoperating Income (Expense)									715	1,239	1,009
Revenues									3,584	890	1,391
Provision for Loan Losses Expensed									465	408	157
Labor and Related Expense									180	573	571
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims									0	0	0
Other Noninterest Expense									899	1,261	1,247
Noninterest Expense									1,079	1,834	1,818
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									2,040	(1,352)	(584)
Income Tax Expense (Benefit)									337	(279)	(267)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									1,703	(1,073)	(317)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									7	(39)	356
Undistributed income of bank subsidiaries									(1,168)	1,273	581
Undistributed income of nonbank subsidiaries									387	906	669
Net Income (Loss) Attributable to Parent									929	1,067	1,289
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									106	(110)	(165)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									1,035	957	1,124
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									0	0	0
Interest and Fee Income, Loans and Leases Held-for-sale											0
Interest and Dividend Income, Securities, Operating									0	0	0
Interest Income, Deposits with Financial Institutions									0	0	0
Operating Leases, Income Statement, Lease Revenue									0	0	0
Total financing revenue and other interest income									0	0	0
Interest Expense, Deposits									0	0	0
Interest Expense, Short-term Borrowings									0	0	0
Interest Expense, Long-term Debt									0	0	0
Interest Expense, Related Party									0	0	0
Interest Expense									0	0	0
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease									0	0	0
Net Financing Revenue									0	0	0
Dividends from Bank Subsidiary									3,300		525
Dividends From Non Bank Subsidiary									0	0	0
Insurance Services Revenue									0	0	0
Gain (Loss) on Sales of Loans, Net									0	0	0
Gain (Loss) on Extinguishment of Debt									0	0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									0	0	0
Noninterest Income, Other Operating Income									0	0	0
Nonoperating Income (Expense)									0	0	0
Revenues									3,300	0	525
Provision for Loan Losses Expensed									0	0	0
Labor and Related Expense									0	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims									0	0	0
Other Noninterest Expense									0	0	0
Noninterest Expense									0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									3,300	0	525
Income Tax Expense (Benefit)									0	(82)	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									3,300	82	525
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									0	0	0
Undistributed income of bank subsidiaries									(1,168)	1,273	581
Undistributed income of nonbank subsidiaries									0	(2)	(1)
Net Income (Loss) Attributable to Parent									2,132	1,353	1,105
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									65	(63)	(43)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									2,197	1,290	1,062
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									5,846	5,266	4,653
Interest and Fee Income, Loans and Leases Held-for-sale											40
Interest and Dividend Income, Securities, Operating									601	421	381
Interest Income, Deposits with Financial Institutions									30	9	7
Operating Leases, Income Statement, Lease Revenue									1,856	2,694	3,389
Total financing revenue and other interest income									8,346	8,407	8,502
Interest Expense, Deposits									1,078	822	708
Interest Expense, Short-term Borrowings									67	17	9
Interest Expense, Long-term Debt									552	581	541
Interest Expense, Related Party									12	11	17
Interest Expense									1,709	1,431	1,275
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease									1,233	1,755	2,242
Net Financing Revenue									5,404	5,221	4,985
Dividends from Bank Subsidiary									0		0
Dividends From Non Bank Subsidiary									0	0	0
Insurance Services Revenue									973	945	940
Gain (Loss) on Sales of Loans, Net									28	22	54
Gain (Loss) on Extinguishment of Debt									(6)	(2)	(2)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									102	176	155
Noninterest Income, Other Operating Income									840	937	1,373
Nonoperating Income (Expense)									1,937	2,078	2,520
Revenues									7,341	7,299	7,505
Provision for Loan Losses Expensed									683	509	550
Labor and Related Expense									915	419	842
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims									332	342	293
Other Noninterest Expense									1,892	2,130	2,195
Noninterest Expense									3,139	2,891	3,330
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									3,519	3,899	3,625
Income Tax Expense (Benefit)									244	831	763
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									3,275	3,068	2,862
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									(4)	(5)	36
Undistributed income of bank subsidiaries									0	0	0
Undistributed income of nonbank subsidiaries									0	0	0
Net Income (Loss) Attributable to Parent									3,271	3,063	2,898
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									104	(106)	(172)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									3,375	2,957	2,726
Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									0	0	0
Interest Income, Deposits with Financial Institutions									0	0	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									12	11	17
Interest Income, Deposits with Financial Institutions									4	0	0
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									0	0	0
Interest Income, Deposits with Financial Institutions									0	0	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									6	8	24
Interest Income, Deposits with Financial Institutions									7	9	8
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									0	0	0
Interest and Fee Income, Loans and Leases Held-for-sale											0
Interest and Dividend Income, Securities, Operating									(2)	(3)	0
Interest Income, Deposits with Financial Institutions									0	0	0
Operating Leases, Income Statement, Lease Revenue									0	0	0
Total financing revenue and other interest income									(31)	(31)	(49)
Interest Expense, Deposits									(4)	0	0
Interest Expense, Short-term Borrowings									0	0	0
Interest Expense, Long-term Debt									0	0	0
Interest Expense, Related Party									(27)	(31)	(49)
Interest Expense									(31)	(31)	(49)
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease									0	0	0
Net Financing Revenue									0	0	0
Dividends from Bank Subsidiary									(6,600)		(1,050)
Dividends From Non Bank Subsidiary									(752)	(965)	(1,123)
Insurance Services Revenue									0	0	0
Gain (Loss) on Sales of Loans, Net									0	0	0
Gain (Loss) on Extinguishment of Debt									0	0	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments									0	9	0
Noninterest Income, Other Operating Income									(1,108)	(1,796)	(2,387)
Nonoperating Income (Expense)									(1,108)	(1,787)	(2,387)
Revenues									(8,460)	(2,752)	(4,560)
Provision for Loan Losses Expensed									0	0	0
Labor and Related Expense									0	0	(450)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims									0	0	0
Other Noninterest Expense									(1,108)	(1,786)	(1,937)
Noninterest Expense									(1,108)	(1,786)	(2,387)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									(7,352)	(966)	(2,173)
Income Tax Expense (Benefit)									0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									(7,352)	(966)	(2,173)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									0	0	0
Undistributed income of bank subsidiaries									2,336	(2,546)	(1,162)
Undistributed income of nonbank subsidiaries									(387)	(904)	(668)
Net Income (Loss) Attributable to Parent									(5,403)	(4,416)	(4,003)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(169)	169	215
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									(5,572)	(4,247)	(3,788)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases									(18)	(19)	(41)
Interest Income, Deposits with Financial Institutions									$ (11)	$ (9)	$ (8)