Asset Quality - Breakdown of Allowance for Loan and Lease Losses and Corresponding Loan Balances (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	$ 35	$ 21
Collectively Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	869	871
Purchased Credit Impaired Allowance, Total ALLL - Including Discontinued Operations	6	5
Loans Outstanding, Total ALLL - Including Discontinued Operations	95,511	90,625
Individually Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	552	470
Collectively Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	94,513	89,580
Purchased Credit Impaired Outstanding, Total ALLL - Including Discontinued Operations	446	575
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	33	19
Collectively Evaluated for Impairment Allowance	861	859
Purchase Credit Impairment Allowance	6	5
Loans Outstanding	94,646	89,552
Individually Evaluated for Impairment Outstanding	529	447
Collectively Evaluated for Impairment Outstanding	93,671	88,530
Purchase Credit Impairment Outstanding	446	575
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	2	2
Collectively Evaluated for Impairment Allowance	8	12
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	865	1,073
Individually Evaluated for Impairment Outstanding	23	23
Collectively Evaluated for Impairment Outstanding	842	1,050
Purchase Credit Impairment Outstanding	0	0
Loans carried at fair value	2
Commercial Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	17	5
Collectively Evaluated for Impairment Allowance	731	734
Purchase Credit Impairment Allowance	3	4
Loans Outstanding	68,032	66,310
Individually Evaluated for Impairment Outstanding	318	228
Collectively Evaluated for Impairment Outstanding	67,541	65,841
Purchase Credit Impairment Outstanding	173	241
Commercial Loans [Member] \| Commercial, Financial and Agricultural [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	17	5
Collectively Evaluated for Impairment Allowance	533	526
Purchase Credit Impairment Allowance	1	1
Loans Outstanding	48,295	45,753
Individually Evaluated for Impairment Outstanding	253	162
Collectively Evaluated for Impairment Outstanding	47,994	45,530
Purchase Credit Impairment Outstanding	48	61
Commercial Loans [Member] \| Commercial Real Estate: Commercial Mortgage [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	141	139
Purchase Credit Impairment Allowance	2	3
Loans Outstanding	13,491	14,285
Individually Evaluated for Impairment Outstanding	65	66
Collectively Evaluated for Impairment Outstanding	13,302	14,041
Purchase Credit Impairment Outstanding	124	178
Commercial Loans [Member] \| Commercial Real Estate: Construction [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	22	33
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,558	1,666
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	1,557	1,664
Purchase Credit Impairment Outstanding	1	2
Commercial Loans [Member] \| Commercial Real Estate Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	163	172
Purchase Credit Impairment Allowance	2	3
Loans Outstanding	15,049	15,951
Individually Evaluated for Impairment Outstanding	65	66
Collectively Evaluated for Impairment Outstanding	14,859	15,705
Purchase Credit Impairment Outstanding	125	180
Commercial Loans [Member] \| Commercial Lease Financing [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	35	36
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	4,688	4,606
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	4,688	4,606
Purchase Credit Impairment Outstanding	0	0
Consumer Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	16	14
Collectively Evaluated for Impairment Allowance	130	125
Purchase Credit Impairment Allowance	3	1
Loans Outstanding	26,614	23,242
Individually Evaluated for Impairment Outstanding	211	219
Collectively Evaluated for Impairment Outstanding	26,130	22,689
Purchase Credit Impairment Outstanding	273	334
Consumer Loans [Member] \| Real Estate - Residential Mortgage [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	4	3
Collectively Evaluated for Impairment Allowance	1	4
Purchase Credit Impairment Allowance	2	0
Loans Outstanding	7,023	5,513
Individually Evaluated for Impairment Outstanding	43	49
Collectively Evaluated for Impairment Outstanding	6,723	5,150
Purchase Credit Impairment Outstanding	257	314
Consumer Loans [Member] \| Home Equity Loan [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	9	8
Collectively Evaluated for Impairment Allowance	21	26
Purchase Credit Impairment Allowance	1	1
Loans Outstanding	10,274	11,142
Individually Evaluated for Impairment Outstanding	126	127
Collectively Evaluated for Impairment Outstanding	10,135	10,998
Purchase Credit Impairment Outstanding	13	17
Consumer Loans [Member] \| Consumer Direct Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	34	30
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	3,513	1,809
Individually Evaluated for Impairment Outstanding	4	4
Collectively Evaluated for Impairment Outstanding	3,506	1,802
Purchase Credit Impairment Outstanding	3	3
Consumer Loans [Member] \| Credit Card Receivable [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	47	48
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,130	1,144
Individually Evaluated for Impairment Outstanding	3	3
Collectively Evaluated for Impairment Outstanding	1,127	1,141
Purchase Credit Impairment Outstanding	0	0
Consumer Loans [Member] \| Consumer Indirect Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment Allowance	3	3
Collectively Evaluated for Impairment Allowance	27	17
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	4,674	3,634
Individually Evaluated for Impairment Outstanding	35	36
Collectively Evaluated for Impairment Outstanding	4,639	3,598
Purchase Credit Impairment Outstanding	0	0
Education Lending [Member] \| Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans carried at fair value	$ 2	$ 2

Allowance for credit impairment.

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Financing receivable allowance for credit losses collectively evaluated for impairment total ALLL including discontinued operations.

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Financing receivable allowance for credit losses individually evaluated for impairment total ALLL including discontinued operations.

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Financing receivable collectively evaluated for impairment total all including discontinued operations.

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Financing receivable individually evaluated for impairment total all including discontinued operations.

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Loans total ALLL including discontinued operations.

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Loans and leases receivable, including loans at fair value net of deferred income.

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Purchased credit impaired loans allowance including discontinued operations.

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Purchased credit impaired loans outstanding principal balance.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The balance of financing receivables that were collectively evaluated for impairment.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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