Fair Value of Assets and Liabilities - Summary Of Book Value And Estimated Fair Value Of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	$ 60,966	$ 60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,885	1,328
Securities purchased under agreements to resell	453	519
Trading securities	1,161	1,412
Loans held for sale:	395	502
Securities available for sale at fair value	8,148	8,391
Securities held to maturity	1,311	1,323
Derivative assets	650	576
Other Assets Financial Instruments [Abstract]
Total assets	81,799	81,661
Liabilities:
Trading liabilities	467	509
Short Term Financial Liabilities [Abstract]
Securities sold under agreements to repurchase	1,828	1,921
Long-Term Debt, Unclassified [Abstract]
Other long-term borrowings	1,165	1,150
Derivative liabilities	795	675
Total liabilities	72,626	72,370
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Long-Term Debt, Unclassified [Abstract]
Restricted investments	31	24
Fair Value, Inputs, Level 3 | FRB Stock
Long-Term Debt, Unclassified [Abstract]
Restricted investments	203	203
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	60,966	60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,885	1,328
Federal funds sold	364	200
Securities purchased under agreements to resell	453	519
Total short-term financial assets	2,702	2,047
Trading securities	1,161	1,412
Loans held for sale:	395	502
Securities available for sale at fair value	8,148	8,391
Securities held to maturity	1,311	1,323
Derivative assets	650	577
Other Assets Financial Instruments [Abstract]
Tax credit investments	662	665
Deferred compensation mutual funds	107	102
Equity, mutual funds, and other	268	261
Total other assets	1,037	1,028
Total assets	76,370	75,799
Liabilities:
Defined maturity deposits	6,297	6,804
Trading liabilities	467	509
Short Term Financial Liabilities [Abstract]
Federal funds purchased	309	302
Securities sold under agreements to repurchase	1,828	1,921
Other short-term borrowings	566	326
Total short-term financial liabilities	2,703	2,549
Long-Term Debt, Unclassified [Abstract]
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	76	65
Secured borrowings	6	3
Junior subordinated debentures	150	150
Other long-term borrowings	886	885
Total term borrowings	1,165	1,150
Derivative liabilities	816	699
Total liabilities	11,448	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	32,563	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	14,245	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	13,414	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	744	764
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	84	68
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	284	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	59,173	58,851
Short-term financial assets:
Interest-bearing deposits with banks	1,885	1,328
Federal funds sold	364	200
Securities purchased under agreements to resell	453	519
Total short-term financial assets	2,702	2,047
Trading securities	1,161	1,412
Loans held for sale:	395	503
Securities available for sale at fair value	8,148	8,391
Securities held to maturity	1,131	1,161
Derivative assets	650	577
Other Assets Financial Instruments [Abstract]
Tax credit investments	652	653
Deferred compensation mutual funds	107	102
Equity, mutual funds, and other	268	261
Total other assets	1,027	1,016
Total assets	74,387	73,958
Liabilities:
Defined maturity deposits	6,333	6,851
Trading liabilities	467	509
Short Term Financial Liabilities [Abstract]
Federal funds purchased	309	302
Securities sold under agreements to repurchase	1,828	1,921
Other short-term borrowings	566	326
Total short-term financial liabilities	2,703	2,549
Long-Term Debt, Unclassified [Abstract]
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	71	60
Secured borrowings	6	3
Junior subordinated debentures	150	150
Other long-term borrowings	843	824
Total term borrowings	1,117	1,084
Derivative liabilities	816	699
Total liabilities	11,436	11,692
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	7	8
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	31,961	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	13,968	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	12,536	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	708	742
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	84	68
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	284	407
Estimate of Fair Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	27	28
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	1,885	1,328
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,885	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	5	9
Other Assets Financial Instruments [Abstract]
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	2,031	1,473
Liabilities:
Defined maturity deposits	0	0
Trading liabilities	0	0
Short Term Financial Liabilities [Abstract]
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
Long-Term Debt, Unclassified [Abstract]
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	4	10
Total liabilities	4	10
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]
Net loans and leases	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]
Net loans and leases	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]
Net loans and leases	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]
Net loans and leases	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 | USDA & SBA 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]
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	364	200
Securities purchased under agreements to resell	453	519
Total short-term financial assets	817	719
Trading securities	1,142	1,399
Loans held for sale:	354	449
Securities available for sale at fair value	8,148	8,391
Securities held to maturity	1,131	1,161
Derivative assets	645	568
Other Assets Financial Instruments [Abstract]
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	12,237	12,687
Liabilities:
Defined maturity deposits	6,333	6,851
Trading liabilities	467	509
Short Term Financial Liabilities [Abstract]
Federal funds purchased	309	302
Securities sold under agreements to repurchase	1,828	1,921
Other short-term borrowings	566	326
Total short-term financial liabilities	2,703	2,549
Long-Term Debt, Unclassified [Abstract]
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	843	824
Total term borrowings	843	824
Derivative liabilities	792	666
Total liabilities	11,138	11,399
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]
Net loans and leases	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]
Net loans and leases	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]
Net loans and leases	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]
Net loans and leases	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:	70	42
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	284	407
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]
Net loans and leases	59,173	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	19	13
Loans held for sale:	41	54
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	0	0
Other Assets Financial Instruments [Abstract]
Tax credit investments	652	653
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	234	227
Total other assets	886	880
Total assets	60,119	59,798
Liabilities:
Defined maturity deposits	0	0
Trading liabilities	0	0
Short Term Financial Liabilities [Abstract]
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
Long-Term Debt, Unclassified [Abstract]
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	71	60
Secured borrowings	6	3
Junior subordinated debentures	150	150
Other long-term borrowings	0	0
Total term borrowings	274	260
Derivative liabilities	20	23
Total liabilities	294	283
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]
Net loans and leases	31,961	31,673
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]
Net loans and leases	13,968	13,831
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]
Net loans and leases	12,536	12,605
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]
Net loans and leases	708	742
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	14	26
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | USDA & SBA 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:	27	28
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	23,227	24,579
Standby and other commitments	$ 780	$ 746