Asset Quality - Breakdown of Allowance for Loan and Lease Losses and Corresponding Loan Balances (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	$ 26	$ 39
Collectively Evaluated for Impairment Allowance, Total ALLL - Including Discontinued Operations	861	838
Purchased Credit Impaired Allowance, Total ALLL - Including Discontinued Operations	6	5
Loans Outstanding, Total ALLL - Including Discontinued Operations	87,719	87,603
Individually Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	375	523
Collectively Evaluated for Impairment Outstanding, Total ALLL - Including Discontinued Operations	86,606	86,215
Purchased Credit Impaired Outstanding, Total ALLL - Including Discontinued Operations	738	865
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	23	37
Collectively Evaluated for Impairment Allowance	848	816
Purchase Credit Impairment Allowance	6	5
Loans Outstanding	86,405	86,038
Individually Evaluated for Impairment Outstanding	354	501
Collectively Evaluated for Impairment Outstanding	85,313	84,672
Purchase Credit Impairment Outstanding	738	865
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	3	2
Collectively Evaluated for Impairment Allowance	13	22
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,314	1,565
Individually Evaluated for Impairment Outstanding	21	22
Collectively Evaluated for Impairment Outstanding	1,293	1,543
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	6	17
Collectively Evaluated for Impairment Allowance	724	694
Purchase Credit Impairment Allowance	5	5
Loans Outstanding	62,733	61,909
Individually Evaluated for Impairment Outstanding	148	289
Collectively Evaluated for Impairment Outstanding	62,228	61,160
Purchase Credit Impairment Outstanding	357	460
Commercial Loans [Member] \| Commercial, Financial and Agricultural [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	6	17
Collectively Evaluated for Impairment Allowance	520	486
Purchase Credit Impairment Allowance	3	5
Loans Outstanding	41,859	39,768
Individually Evaluated for Impairment Outstanding	136	284
Collectively Evaluated for Impairment Outstanding	41,640	39,372
Purchase Credit Impairment Outstanding	83	112
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	131	144
Purchase Credit Impairment Allowance	2	0
Loans Outstanding	14,088	15,111
Individually Evaluated for Impairment Outstanding	12	5
Collectively Evaluated for Impairment Outstanding	13,828	14,784
Purchase Credit Impairment Outstanding	248	322
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	30	22
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,960	2,345
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	1,934	2,319
Purchase Credit Impairment Outstanding	26	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	161	166
Purchase Credit Impairment Allowance	2	0
Loans Outstanding	16,048	17,456
Individually Evaluated for Impairment Outstanding	12	5
Collectively Evaluated for Impairment Outstanding	15,762	17,103
Purchase Credit Impairment Outstanding	274	348
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	43	42
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	4,826	4,685
Individually Evaluated for Impairment Outstanding	0	0
Collectively Evaluated for Impairment Outstanding	4,826	4,685
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	17	20
Collectively Evaluated for Impairment Allowance	124	122
Purchase Credit Impairment Allowance	1	0
Loans Outstanding	23,672	24,129
Individually Evaluated for Impairment Outstanding	206	212
Collectively Evaluated for Impairment Outstanding	23,085	23,512
Purchase Credit Impairment Outstanding	381	405
Consumer Loans [Member] \| Real Estate - Residential Mortgage [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	5	2
Collectively Evaluated for Impairment Allowance	2	15
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	5,483	5,547
Individually Evaluated for Impairment Outstanding	49	51
Collectively Evaluated for Impairment Outstanding	5,079	5,128
Purchase Credit Impairment Outstanding	355	368
Consumer Loans [Member] \| Home Equity Loan [Member] \| Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment Allowance	9	17
Collectively Evaluated for Impairment Allowance	33	37
Purchase Credit Impairment Allowance	1	0
Loans Outstanding	12,028	12,674
Individually Evaluated for Impairment Outstanding	117	125
Collectively Evaluated for Impairment Outstanding	11,889	12,519
Purchase Credit Impairment Outstanding	22	30
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	28	24
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,794	1,788
Individually Evaluated for Impairment Outstanding	4	3
Collectively Evaluated for Impairment Outstanding	1,786	1,778
Purchase Credit Impairment Outstanding	4	7
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	44	38
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	1,106	1,111
Individually Evaluated for Impairment Outstanding	2	3
Collectively Evaluated for Impairment Outstanding	1,104	1,108
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	1
Collectively Evaluated for Impairment Allowance	17	8
Purchase Credit Impairment Allowance	0	0
Loans Outstanding	3,261	3,009
Individually Evaluated for Impairment Outstanding	34	30
Collectively Evaluated for Impairment Outstanding	3,227	2,979
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	$ 3

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
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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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The balance of financing receivables that were individually 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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