Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	$ 1,543	$ 1,368
Interest and Dividend Income, Securities, Operating	176	134
Interest Income, Deposits with Financial Institutions	15	5
Operating Leases, Income Statement, Lease Revenue	382	543
Total financing revenue and other interest income	2,116	2,050
Interest Expense, Deposits	351	231
Interest Expense, Short-term Borrowings	32	27
Interest Expense, Long-term Debt	411	424
Interest Expense, Related Party	0	0
Interest Expense	794	682
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	273	389
Net Financing Revenue	1,049	979
Dividends from Bank Subsidiary	0
Dividends From Non Bank Subsidiary	0	0
Insurance Services Revenue	256	241
Gain (Loss) on Sales of Loans, Net	1	14
Gain (Loss) on Investments	(12)	27
Noninterest Income, Other Operating Income	109	114
Nonoperating Income (Expense)	354	396
Revenues	1,403	1,375
Provision for Loan Losses Expensed	261	271
Labor and Related Expense	306	285
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	63	88
Other Noninterest Expense	445	405
Noninterest Expense	814	778
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	328	326
Income Tax Expense (Benefit)	76	113
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	252	213
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(2)	1
Undistributed income of bank subsidiaries	0	0
Undistributed income of nonbank subsidiaries	0	0
Net Income (Loss) Attributable to Parent	250	214
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(328)	20
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(78)	234
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	11	(35)
Interest and Dividend Income, Securities, Operating	0	0
Interest Income, Deposits with Financial Institutions	2	2
Operating Leases, Income Statement, Lease Revenue	2	3
Total financing revenue and other interest income	19	(26)
Interest Expense, Deposits	0	1
Interest Expense, Short-term Borrowings	10	17
Interest Expense, Long-term Debt	258	281
Interest Expense, Related Party	3	4
Interest Expense	271	303
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	4	2
Net Financing Revenue	(256)	(331)
Dividends from Bank Subsidiary	1,000
Dividends From Non Bank Subsidiary	169	41
Insurance Services Revenue	0	0
Gain (Loss) on Sales of Loans, Net	28	(2)
Gain (Loss) on Investments	0	0
Noninterest Income, Other Operating Income	96	268
Nonoperating Income (Expense)	124	266
Revenues	1,037	(24)
Provision for Loan Losses Expensed	81	107
Labor and Related Expense	23	122
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0
Other Noninterest Expense	182	288
Noninterest Expense	205	410
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	751	(541)
Income Tax Expense (Benefit)	(56)	(134)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	807	(407)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(1)	2
Undistributed income of bank subsidiaries	(597)	389
Undistributed income of nonbank subsidiaries	41	230
Net Income (Loss) Attributable to Parent	250	214
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(328)	20
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(78)	234
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0
Interest and Dividend Income, Securities, Operating	0	0
Interest Income, Deposits with Financial Institutions	0	0
Operating Leases, Income Statement, Lease Revenue	0	0
Total financing revenue and other interest income	0	0
Interest Expense, Deposits	0	0
Interest Expense, Short-term Borrowings	0	0
Interest Expense, Long-term Debt	0	0
Interest Expense, Related Party	0	0
Interest Expense	0	0
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	0	0
Net Financing Revenue	0	0
Dividends from Bank Subsidiary	1,000
Dividends From Non Bank Subsidiary	0	0
Insurance Services Revenue	0	0
Gain (Loss) on Sales of Loans, Net	0	0
Gain (Loss) on Investments	0	0
Noninterest Income, Other Operating Income	0	0
Nonoperating Income (Expense)	0	0
Revenues	1,000	0
Provision for Loan Losses Expensed	0	0
Labor and Related Expense	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0
Other Noninterest Expense	0	0
Noninterest Expense	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	1,000	0
Income Tax Expense (Benefit)	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	1,000	0
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
Undistributed income of bank subsidiaries	(597)	389
Undistributed income of nonbank subsidiaries	0	0
Net Income (Loss) Attributable to Parent	403	389
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(276)	5
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	127	394
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1,532	1,403
Interest and Dividend Income, Securities, Operating	176	135
Interest Income, Deposits with Financial Institutions	14	3
Operating Leases, Income Statement, Lease Revenue	380	540
Total financing revenue and other interest income	2,105	2,085
Interest Expense, Deposits	354	230
Interest Expense, Short-term Borrowings	22	10
Interest Expense, Long-term Debt	153	143
Interest Expense, Related Party	2	4
Interest Expense	531	387
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	269	387
Net Financing Revenue	1,305	1,311
Dividends from Bank Subsidiary	0
Dividends From Non Bank Subsidiary	0	0
Insurance Services Revenue	256	241
Gain (Loss) on Sales of Loans, Net	1	16
Gain (Loss) on Investments	(12)	27
Noninterest Income, Other Operating Income	221	223
Nonoperating Income (Expense)	466	507
Revenues	1,771	1,818
Provision for Loan Losses Expensed	208	164
Labor and Related Expense	283	163
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	63	88
Other Noninterest Expense	471	494
Noninterest Expense	817	745
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	746	909
Income Tax Expense (Benefit)	132	247
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	614	662
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(1)	(1)
Undistributed income of bank subsidiaries	0	0
Undistributed income of nonbank subsidiaries	0	0
Net Income (Loss) Attributable to Parent	613	661
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(339)	19
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	274	680
Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0
Interest Income, Deposits with Financial Institutions	0	0
Gain (Loss) on Sales of Loans, Net	0	0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	2	4
Interest Income, Deposits with Financial Institutions	2	0
Gain (Loss) on Sales of Loans, Net	(423)	1,146
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0
Interest Income, Deposits with Financial Institutions	0	0
Gain (Loss) on Sales of Loans, Net	0	0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	1	3
Interest Income, Deposits with Financial Institutions	2	1
Gain (Loss) on Sales of Loans, Net	1	170
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	0	0
Interest and Dividend Income, Securities, Operating	0	(1)
Interest Income, Deposits with Financial Institutions	(1)	0
Operating Leases, Income Statement, Lease Revenue	0	0
Total financing revenue and other interest income	(8)	(9)
Interest Expense, Deposits	(3)	0
Interest Expense, Short-term Borrowings	0	0
Interest Expense, Long-term Debt	0	0
Interest Expense, Related Party	(5)	(8)
Interest Expense	(8)	(8)
Operating Leases, Income Statement, Depreciation Expense on Property Subject to or Held-for-lease	0	0
Net Financing Revenue	0	(1)
Dividends from Bank Subsidiary	(2,000)
Dividends From Non Bank Subsidiary	(169)	(41)
Insurance Services Revenue	0	0
Gain (Loss) on Sales of Loans, Net	(28)	0
Gain (Loss) on Investments	0	0
Noninterest Income, Other Operating Income	(208)	(377)
Nonoperating Income (Expense)	(236)	(377)
Revenues	(2,405)	(419)
Provision for Loan Losses Expensed	(28)	0
Labor and Related Expense	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	0	0
Other Noninterest Expense	(208)	(377)
Noninterest Expense	(208)	(377)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(2,169)	(42)
Income Tax Expense (Benefit)	0	0
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	(2,169)	(42)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	0
Undistributed income of bank subsidiaries	1,194	(778)
Undistributed income of nonbank subsidiaries	(41)	(230)
Net Income (Loss) Attributable to Parent	(1,016)	(1,050)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	615	(24)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(401)	(1,074)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Income Statements, Captions [Line Items]
Interest and Fee Income, Loans and Leases	(3)	(7)
Interest Income, Deposits with Financial Institutions	(4)	(1)
Gain (Loss) on Sales of Loans, Net	$ 422	$ (1,316)