Fair Value of Assets and Liabilities - Summary Of Book Value And Estimated Fair Value Of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	$ 57,686	$ 57,269
Short-term financial assets:
Interest-bearing deposits with banks	11,635	8,351
Securities purchased under agreements to resell	463	380
Trading securities	1,076	1,176
Loans held for sale	811	1,022
Securities available-for-sale	8,351	8,047
Derivative assets	543	765
Other assets:
Total assets	87,513	84,209
Liabilities:
Trading Liabilities	454	353
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,098	1,187
Term borrowings:
Other long term borrowings	1,671	1,670
Gross amounts of recognized liabilities	243	125
Total liabilities	79,206	75,902
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	34	61
Fair Value, Inputs, Level 3 | FRB Stock
Term borrowings:
Restricted investments	202	202
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	57,686	57,269
Short-term financial assets:
Interest-bearing deposits with banks	11,635	8,351
Federal funds sold and securities purchased under agreements to resell	463	65
Securities purchased under agreements to resell	57	380
Total short-term financial assets	12,155	8,796
Trading securities	1,076	1,176
Loans held for sale	811	1,022
Securities available-for-sale	8,351	8,047
Derivative assets	561	770
Other assets:
Tax credit investments	410	400
Deferred compensation assets	122	118
Equity, mutual funds, and other	262	288
Total other assets	794	806
Total assets	81,434	77,886
Liabilities:
Defined maturity	4,653	5,070
Trading Liabilities	454	353
Short-term financial liabilities:
Federal funds purchased	982	845
Securities sold under agreements to repurchase	1,098	1,187
Other short-term borrowings	122	166
Short Term Financial Liabilities	2,202	2,198
Term borrowings:
Real estate investment trust-preferred	46	46
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	239	238
Other long term borrowings	1,326	1,326
Total term borrowings	1,671	1,670
Gross amounts of recognized liabilities	265	149
Total liabilities	9,245	9,440
Reported Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	33,509	32,651
Reported Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	12,238	12,033
Reported Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	10,831	11,483
Reported Value Measurement | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	1,108	1,102
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	449	405
Reported Value Measurement | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	300	509
Reported Value Measurement | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	58	77
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	57,931	57,695
Short-term financial assets:
Interest-bearing deposits with banks	11,635	8,351
Federal funds sold and securities purchased under agreements to resell	463	65
Securities purchased under agreements to resell	57	380
Total short-term financial assets	12,155	8,796
Trading securities	1,076	1,176
Loans held for sale	811	1,025
Securities available-for-sale	8,351	8,047
Derivative assets	561	769
Other assets:
Tax credit investments	400	371
Deferred compensation assets	122	118
Equity, mutual funds, and other	262	288
Total other assets	784	777
Total assets	81,669	78,285
Liabilities:
Defined maturity	4,664	5,083
Trading Liabilities	454	353
Short-term financial liabilities:
Federal funds purchased	982	845
Securities sold under agreements to repurchase	1,098	1,187
Other short-term borrowings	122	166
Short Term Financial Liabilities	2,202	2,198
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	237	223
Other long term borrowings	1,462	1,455
Total term borrowings	1,806	1,785
Gross amounts of recognized liabilities	267	149
Total liabilities	9,393	9,568
Unfunded Commitments:
Loan commitments	1	2
Standby and other commitments	6	6
Estimate of Fair Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	33,249	32,582
Estimate of Fair Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	12,265	12,079
Estimate of Fair Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	11,283	11,903
Estimate of Fair Value Measurement | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	1,134	1,131
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	449	405
Estimate of Fair Value Measurement | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	300	512
Estimate of Fair Value Measurement | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Estimate of Fair Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	58	77
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Short-term financial assets:
Interest-bearing deposits with banks	11,635	8,351
Federal funds sold and securities purchased under agreements to resell	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	11,635	8,351
Trading securities	0	0
Loans held for sale	0	0
Securities available-for-sale	0	0
Derivative assets	145	63
Other assets:
Tax credit investments	0	0
Deferred compensation assets	122	118
Equity, mutual funds, and other	25	25
Total other assets	147	143
Total assets	11,927	8,557
Liabilities:
Defined maturity	0	0
Trading Liabilities	0	0
Short-term financial liabilities:
Federal funds purchased	0	0
Securities sold under agreements to repurchase	0	0
Other short-term borrowings	0	0
Short Term Financial Liabilities	0	0
Term borrowings:
Real estate investment trust-preferred	0	0
Term borrowings—new market tax credit investment	0	0
Secured borrowings	0	0
Junior subordinated debentures	0	0
Other long term borrowings	0	0
Total term borrowings	0	0
Gross amounts of recognized liabilities	116	71
Total liabilities	116	71
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold and securities purchased under agreements to resell	463	65
Securities purchased under agreements to resell	57	380
Total short-term financial assets	520	445
Trading securities	1,076	1,176
Loans held for sale	740	935
Securities available-for-sale	8,329	8,015
Derivative assets	416	706
Other assets:
Tax credit investments	0	0
Deferred compensation assets	0	0
Equity, mutual funds, and other	0	0
Total other assets	0	0
Total assets	11,081	11,277
Liabilities:
Defined maturity	4,664	5,083
Trading Liabilities	454	353
Short-term financial liabilities:
Federal funds purchased	982	845
Securities sold under agreements to repurchase	1,098	1,187
Other short-term borrowings	122	166
Short Term Financial Liabilities	2,202	2,198
Term borrowings:
Real estate investment trust-preferred	0	0
Term borrowings—new market tax credit investment	0	0
Secured borrowings	0	0
Junior subordinated debentures	0	0
Other long term borrowings	1,462	1,455
Total term borrowings	1,462	1,455
Gross amounts of recognized liabilities	130	64
Total liabilities	8,912	9,153
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	437	393
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	299	511
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	57,931	57,695
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold and securities purchased under agreements to resell	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	0	0
Trading securities	0	0
Loans held for sale	71	90
Securities available-for-sale	22	32
Derivative assets	0	0
Other assets:
Tax credit investments	400	371
Deferred compensation assets	0	0
Equity, mutual funds, and other	237	263
Total other assets	637	634
Total assets	58,661	58,451
Liabilities:
Defined maturity	0	0
Trading Liabilities	0	0
Short-term financial liabilities:
Federal funds purchased	0	0
Securities sold under agreements to repurchase	0	0
Other short-term borrowings	0	0
Short Term Financial Liabilities	0	0
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	237	223
Other long term borrowings	0	0
Total term borrowings	344	330
Gross amounts of recognized liabilities	21	14
Total liabilities	365	344
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	33,249	32,582
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	12,265	12,079
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	11,283	11,903
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loans, net of unearned income and allowance for loan losses	1,134	1,131
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	12	12
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	1	1
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	58	77
Contractual Amount
Unfunded Commitments:
Loan commitments	20,881	20,796
Standby and other commitments	$ 720	$ 751