Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	$ 61,622	$ 60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,286	1,328
Securities purchased under agreements to resell	796	519
Trading securities	1,549	1,412
Loans held for sale:	494	502
Securities available for sale at fair value	8,248	8,391
Securities held to maturity	1,282	1,323
Derivative assets	437	576
Other assets:
Total assets	82,635	81,661
Liabilities:
Trading liabilities	767	509
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,611	1,921
Term borrowings:
Other long-term borrowings	1,202	1,150
Derivative liabilities	488	675
Total liabilities	73,319	72,370
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	47	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	61,622	60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,286	1,328
Federal funds sold	212	200
Securities purchased under agreements to resell	796	519
Total short-term financial assets	2,294	2,047
Trading securities	1,549	1,412
Loans held for sale:	494	502
Securities available for sale at fair value	8,248	8,391
Securities held to maturity	1,282	1,323
Derivative assets	437	577
Other assets:
Tax credit investments	690	665
Deferred compensation mutual funds	110	102
Equity, mutual funds, and other	285	261
Total other assets	1,085	1,028
Total assets	77,011	75,799
Liabilities:
Defined maturity deposits	8,326	6,804
Trading liabilities	767	509
Short-term financial liabilities:
Federal funds purchased	300	302
Securities sold under agreements to repurchase	1,610	1,921
Other short-term borrowings	675	326
Total short-term financial liabilities	2,585	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investments	83	65
Secured borrowings	35	3
Junior subordinated debentures	151	150
Other long-term borrowings	886	885
Total term borrowings	1,202	1,150
Derivative liabilities	521	699
Total liabilities	13,401	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	32,740	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	14,487	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	13,731	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	664	764
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	87	68
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	379	406
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	28	28
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	60,549	58,851
Short-term financial assets:
Interest-bearing deposits with banks	1,286	1,328
Federal funds sold	212	200
Securities purchased under agreements to resell	796	519
Total short-term financial assets	2,294	2,047
Trading securities	1,549	1,412
Loans held for sale:	495	503
Securities available for sale at fair value	8,248	8,391
Securities held to maturity	1,144	1,161
Derivative assets	437	577
Other assets:
Tax credit investments	668	653
Deferred compensation mutual funds	110	102
Equity, mutual funds, and other	285	261
Total other assets	1,063	1,016
Total assets	75,779	73,958
Liabilities:
Defined maturity deposits	8,319	6,851
Trading liabilities	767	509
Short-term financial liabilities:
Federal funds purchased	300	302
Securities sold under agreements to repurchase	1,610	1,921
Other short-term borrowings	675	326
Total short-term financial liabilities	2,585	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investments	81	60
Secured borrowings	35	3
Junior subordinated debentures	150	150
Other long-term borrowings	879	824
Total term borrowings	1,192	1,084
Derivative liabilities	521	699
Total liabilities	13,384	11,692
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	8	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	1,286	1,328
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,286	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	110	102
Equity, mutual funds, and other	35	34
Total other assets	145	136
Total assets	1,437	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 investments	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	212	200
Securities purchased under agreements to resell	796	519
Total short-term financial assets	1,008	719
Trading securities	1,532	1,399
Loans held for sale:	451	449
Securities available for sale at fair value	8,248	8,391
Securities held to maturity	1,144	1,161
Derivative assets	431	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	12,814	12,687
Liabilities:
Defined maturity deposits	8,319	6,851
Trading liabilities	767	509
Short-term financial liabilities:
Federal funds purchased	300	302
Securities sold under agreements to repurchase	1,610	1,921
Other short-term borrowings	675	326
Total short-term financial liabilities	2,585	2,549
Term borrowings:
Real estate investment trust-preferred	0	0
Term borrowings—new market tax credit investments	0	0
Secured borrowings	0	0
Junior subordinated debentures	0	0
Other long-term borrowings	879	824
Total term borrowings	879	824
Derivative liabilities	484	666
Total liabilities	13,034	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	60,549	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	17	13
Loans held for sale:	44	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	668	653
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	250	227
Total other assets	918	880
Total assets	61,528	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 investments	81	60
Secured borrowings	35	3
Junior subordinated debentures	150	150
Other long-term borrowings	0	0
Total term borrowings	313	260
Derivative liabilities	32	23
Total liabilities	345	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	32,231	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	32,231	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	14,262	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	14,262	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	13,374	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	13,374	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	682	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	682	742
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	87	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:	71	42
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	16	26
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	380	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:	380	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:	28	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:	28	28
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	21,379	24,579
Standby and other commitments	$ 737	$ 746