Asset Quality - Breakdown of Allowance for Loan and Lease Losses and Corresponding Loan Balances (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	$ 21	$ 26
Collectively Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	871	861
Purchased Credit Impaired Allowance, Total ALLL - Including Discontinued Operations	5	6
Loans Outstanding, Total ALLL - Including Discontinued Operations	90,625	87,719
Individually Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	470	375
Collectively Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	89,580	86,606
Purchased Credit Impaired Outstanding, Total ALLL - Including Discontinued Operations	575	738
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	19	23
Collectively Evaluated for Impairment Allowance	859	848
Purchase Credit Impairment Allowance	5	6
Loans Outstanding	89,552	86,405
Individually Evaluated for Impairment Outstanding	447	354
Collectively Evaluated for Impairment Outstanding	88,530	85,313
Purchase Credit Impairment Outstanding	575	738
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	2	3
Collectively Evaluated for Impairment Allowance	12	13
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,073	1,314
Individually Evaluated for Impairment Outstanding	23	21
Collectively Evaluated for Impairment Outstanding	1,050	1,293
Purchase Credit Impairment Outstanding	0	0
Loans carried at fair value	2
Commercial Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	5	6
Collectively Evaluated for Impairment Allowance	734	724
Purchase Credit Impairment Allowance	4	5
Loans Outstanding	66,310	62,733
Individually Evaluated for Impairment Outstanding	228	148
Collectively Evaluated for Impairment Outstanding	65,841	62,228
Purchase Credit Impairment Outstanding	241	357
Commercial Loans [Member] \| Commercial, Financial and Agricultural [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	5	6
Collectively Evaluated for Impairment Allowance	526	520
Purchase Credit Impairment Allowance	1	3
Loans Outstanding	45,753	41,859
Individually Evaluated for Impairment Outstanding	162	136
Collectively Evaluated for Impairment Outstanding	45,530	41,640
Purchase Credit Impairment Outstanding	61	83
Commercial Loans [Member] \| Commercial Real Estate: Commercial Mortgage [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	139	131
Purchase Credit Impairment Allowance	3	2
Loans Outstanding	14,285	14,088
Individually Evaluated for Impairment Outstanding	66	12
Collectively Evaluated for Impairment Outstanding	14,041	13,828
Purchase Credit Impairment Outstanding	178	248
Commercial Loans [Member] \| Commercial Real Estate: Construction [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	33	30
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,666	1,960
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	1,664	1,934
Purchase Credit Impairment Outstanding	2	26
Commercial Loans [Member] \| Commercial Real Estate Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	172	161
Purchase Credit Impairment Allowance	3	2
Loans Outstanding	15,951	16,048
Individually Evaluated for Impairment Outstanding	66	12
Collectively Evaluated for Impairment Outstanding	15,705	15,762
Purchase Credit Impairment Outstanding	180	274
Commercial Loans [Member] \| Commercial Lease Financing [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	36	43
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	4,606	4,826
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	4,606	4,826
Purchase Credit Impairment Outstanding	0	0
Consumer Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	14	17
Collectively Evaluated for Impairment Allowance	125	124
Purchase Credit Impairment Allowance	1	1
Loans Outstanding	23,242	23,672
Individually Evaluated for Impairment Outstanding	219	206
Collectively Evaluated for Impairment Outstanding	22,689	23,085
Purchase Credit Impairment Outstanding	334	381
Consumer Loans [Member] \| Real Estate - Residential Mortgage [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	3	5
Collectively Evaluated for Impairment Allowance	4	2
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	5,513	5,483
Individually Evaluated for Impairment Outstanding	49	49
Collectively Evaluated for Impairment Outstanding	5,150	5,079
Purchase Credit Impairment Outstanding	314	355
Consumer Loans [Member] \| Home Equity Loan [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	8	9
Collectively Evaluated for Impairment Allowance	26	33
Purchase Credit Impairment Allowance	1	1
Loans Outstanding	11,142	12,028
Individually Evaluated for Impairment Outstanding	127	117
Collectively Evaluated for Impairment Outstanding	10,998	11,889
Purchase Credit Impairment Outstanding	17	22
Consumer Loans [Member] \| Consumer Direct Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	30	28
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,809	1,794
Individually Evaluated for Impairment Outstanding	4	4
Collectively Evaluated for Impairment Outstanding	1,802	1,786
Purchase Credit Impairment Outstanding	3	4
Consumer Loans [Member] \| Credit Card Receivable [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	0	0
Collectively Evaluated for Impairment Allowance	48	44
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,144	1,106
Individually Evaluated for Impairment Outstanding	3	2
Collectively Evaluated for Impairment Outstanding	1,141	1,104
Purchase Credit Impairment Outstanding	0	0
Consumer Loans [Member] \| Consumer Indirect Loans [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	3	3
Collectively Evaluated for Impairment Allowance	17	17
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	3,634	3,261
Individually Evaluated for Impairment Outstanding	36	34
Collectively Evaluated for Impairment Outstanding	3,598	3,227
Purchase Credit Impairment Outstanding	0	0
Education Lending [Member] \| Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [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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