Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	$ 61,960	$ 60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,452	1,328
Securities purchased under agreements to resell	424	519
Trading securities	1,249	1,412
Loans held for sale:	471	502
Securities available for sale at fair value	7,924	8,391
Securities held to maturity	1,297	1,323
Derivative assets	639	576
Other assets:
Total assets	82,230	81,661
Liabilities:
Trading liabilities	423	509
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,948	1,921
Term borrowings:
Other long-term borrowings	1,175	1,150
Derivative liabilities	789	675
Total liabilities	73,275	72,370
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	86	24
Fair Value, Inputs, Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	203
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	61,960	60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,452	1,328
Federal funds sold	63	200
Securities purchased under agreements to resell	424	519
Total short-term financial assets	1,939	2,047
Trading securities	1,249	1,412
Loans held for sale:	471	502
Securities available for sale at fair value	7,924	8,391
Securities held to maturity	1,297	1,323
Derivative assets	640	577
Other assets:
Tax credit investments	668	665
Deferred compensation mutual funds	107	102
Equity, mutual funds, and other	323	261
Total other assets	1,098	1,028
Total assets	76,578	75,799
Liabilities:
Defined maturity deposits	7,163	6,804
Trading liabilities	423	509
Short-term financial liabilities:
Federal funds purchased	624	302
Securities sold under agreements to repurchase	1,948	1,921
Other short-term borrowings	1,943	326
Total short-term financial liabilities	4,515	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	83	65
Secured borrowings	9	3
Junior subordinated debentures	151	150
Other long-term borrowings	885	885
Total term borrowings	1,175	1,150
Derivative liabilities	808	699
Total liabilities	14,084	11,711
Reported Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	33,108	32,294
Reported Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	14,448	14,044
Reported Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	13,678	13,417
Reported Value Measurement | Credit card and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	726	764
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	117	68
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	327	406
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	27	28
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	60,362	58,851
Short-term financial assets:
Interest-bearing deposits with banks	1,452	1,328
Federal funds sold	63	200
Securities purchased under agreements to resell	424	519
Total short-term financial assets	1,939	2,047
Trading securities	1,249	1,412
Loans held for sale:	471	503
Securities available for sale at fair value	7,924	8,391
Securities held to maturity	1,108	1,161
Derivative assets	640	577
Other assets:
Tax credit investments	656	653
Deferred compensation mutual funds	107	102
Equity, mutual funds, and other	323	261
Total other assets	1,086	1,016
Total assets	74,779	73,958
Liabilities:
Defined maturity deposits	7,205	6,851
Trading liabilities	423	509
Short-term financial liabilities:
Federal funds purchased	624	302
Securities sold under agreements to repurchase	1,948	1,921
Other short-term borrowings	1,943	326
Total short-term financial liabilities	4,515	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	78	60
Secured borrowings	9	3
Junior subordinated debentures	150	150
Other long-term borrowings	847	824
Total term borrowings	1,131	1,084
Derivative liabilities	808	699
Total liabilities	14,082	11,692
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	7	8
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	1,452	1,328
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,452	1,328
Trading securities	0	0
Loans held for sale:	0	0
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	6	9
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	107	102
Equity, mutual funds, and other	34	34
Total other assets	141	136
Total assets	1,599	1,473
Liabilities:
Defined maturity deposits	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
Total 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
Derivative liabilities	5	10
Total liabilities	5	10
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	63	200
Securities purchased under agreements to resell	424	519
Total short-term financial assets	487	719
Trading securities	1,233	1,399
Loans held for sale:	429	449
Securities available for sale at fair value	7,924	8,391
Securities held to maturity	1,108	1,161
Derivative assets	634	568
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	0	0
Total other assets	0	0
Total assets	11,815	12,687
Liabilities:
Defined maturity deposits	7,205	6,851
Trading liabilities	423	509
Short-term financial liabilities:
Federal funds purchased	624	302
Securities sold under agreements to repurchase	1,948	1,921
Other short-term borrowings	1,943	326
Total short-term financial liabilities	4,515	2,549
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	847	824
Total term borrowings	847	824
Derivative liabilities	785	666
Total liabilities	13,775	11,399
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	60,362	58,851
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	0	0
Trading securities	16	13
Loans held for sale:	42	54
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	0	0
Other assets:
Tax credit investments	656	653
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	289	227
Total other assets	945	880
Total assets	61,365	59,798
Liabilities:
Defined maturity deposits	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
Total short-term financial liabilities	0	0
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	78	60
Secured borrowings	9	3
Junior subordinated debentures	150	150
Other long-term borrowings	0	0
Total term borrowings	284	260
Derivative liabilities	18	23
Total liabilities	302	283
Estimate of Fair Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	32,427	31,673
Estimate of Fair Value Measurement | Commercial, financial and industrial | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial and industrial | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial and industrial | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	32,427	31,673
Estimate of Fair Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	14,214	13,831
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	14,214	13,831
Estimate of Fair Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	13,004	12,605
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	13,004	12,605
Estimate of Fair Value Measurement | Credit card and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	717	742
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	717	742
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	117	68
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 2
Short-term financial assets:
Loans held for sale:	102	42
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	15	26
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	327	407
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | Fair Value, Inputs, Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | Fair Value, Inputs, Level 2
Short-term financial assets:
Loans held for sale:	327	407
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	27	28
Estimate of Fair Value Measurement | Mortgage loans - LOCOM | Fair Value, Inputs, Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans - LOCOM | Fair Value, Inputs, Level 2
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans - LOCOM | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	27	28
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	21,990	24,579
Standby and other commitments	$ 752	$ 746