Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets
Total loans and leases, net of allowance for loan and lease losses	$ 61,750	$ 60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,538	1,328
Securities purchased under agreements to resell	572	519
Trading securities:	1,387	1,412
Loans held for sale:	551	502
Securities held to maturity	1,270	1,323
Derivative assets	530	576
Other assets:
Total assets	82,152	81,661
Liabilities:
Trading liabilities	550	509
Short-term financial liabilities:
Securities sold under agreements to repurchase	2,096	1,921
Term borrowings:
Other long-term borrowings	1,195	1,150
Derivative liabilities	655	675
Total liabilities	73,041	72,370
Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	51	24
Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	203
Reported Value Measurement
Assets
Total loans and leases, net of allowance for loan and lease losses	61,750	60,519
Short-term financial assets:
Interest-bearing deposits with banks	1,538	1,328
Federal funds sold	59	200
Securities purchased under agreements to resell	572	519
Total short-term financial assets	2,169	2,047
Trading securities:	1,387	1,412
Loans held for sale:	551	502
Securities available for sale at fair value	7,896	8,391
Securities held to maturity	1,270	1,323
Derivative assets	531	577
Other assets:
Tax credit investments	706	665
Deferred compensation mutual funds	111	102
Equity, mutual funds, and other	289	261
Total other assets	1,106	1,028
Total assets	76,660	75,799
Liabilities:
Defined maturity	6,613	6,804
Trading liabilities	550	509
Short-term financial liabilities:
Federal funds purchased	259	302
Securities sold under agreements to repurchase	2,096	1,921
Other short-term borrowings	1,045	326
Total short-term financial liabilities	3,400	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investments	74	65
Secured borrowings	37	3
Junior subordinated debentures	151	150
Other long-term borrowings	886	885
Total term borrowings	1,195	1,150
Derivative liabilities	671	699
Total liabilities	12,429	11,711
Reported Value Measurement | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	33,083	32,294
Reported Value Measurement | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	14,194	14,044
Reported Value Measurement | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,826	13,417
Reported Value Measurement | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	647	764
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	85	68
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	439	406
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	27	28
Estimate of Fair Value Measurement
Assets
Total loans and leases, net of allowance for loan and lease losses	60,324	58,851
Short-term financial assets:
Interest-bearing deposits with banks	1,538	1,328
Federal funds sold	59	200
Securities purchased under agreements to resell	572	519
Total short-term financial assets	2,169	2,047
Trading securities:	1,387	1,412
Loans held for sale:	551	503
Securities available for sale at fair value	7,896	8,391
Securities held to maturity	1,083	1,161
Derivative assets	531	577
Other assets:
Tax credit investments	692	653
Deferred compensation mutual funds	111	102
Equity, mutual funds, and other	289	261
Total other assets	1,092	1,016
Total assets	75,033	73,958
Liabilities:
Defined maturity	6,591	6,851
Trading liabilities	550	509
Short-term financial liabilities:
Federal funds purchased	259	302
Securities sold under agreements to repurchase	2,096	1,921
Other short-term borrowings	1,045	326
Total short-term financial liabilities	3,400	2,549
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investments	70	60
Secured borrowings	37	3
Junior subordinated debentures	142	150
Other long-term borrowings	866	824
Total term borrowings	1,162	1,084
Derivative liabilities	671	699
Total liabilities	12,374	11,692
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	9	8
Estimate of Fair Value Measurement | Level 1
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Short-term financial assets:
Interest-bearing deposits with banks	1,538	1,328
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,538	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	8	9
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	111	102
Equity, mutual funds, and other	35	34
Total other assets	146	136
Total assets	1,692	1,473
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
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	6	10
Total liabilities	6	10
Estimate of Fair Value Measurement | Level 2
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	59	200
Securities purchased under agreements to resell	572	519
Total short-term financial assets	631	719
Trading securities:	1,364	1,399
Loans held for sale:	508	449
Securities available for sale at fair value	7,896	8,391
Securities held to maturity	1,083	1,161
Derivative assets	523	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	12,005	12,687
Liabilities:
Defined maturity	6,591	6,851
Trading liabilities	550	509
Short-term financial liabilities:
Federal funds purchased	259	302
Securities sold under agreements to repurchase	2,096	1,921
Other short-term borrowings	1,045	326
Total short-term financial liabilities	3,400	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	866	824
Total term borrowings	866	824
Derivative liabilities	650	666
Total liabilities	12,057	11,399
Estimate of Fair Value Measurement | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	60,324	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:	23	13
Loans held for sale:	43	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	692	653
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	254	227
Total other assets	946	880
Total assets	61,336	59,798
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
Total short-term financial liabilities	0	0
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investments	70	60
Secured borrowings	37	3
Junior subordinated debentures	142	150
Other long-term borrowings	0	0
Total term borrowings	296	260
Derivative liabilities	15	23
Total liabilities	311	283
Estimate of Fair Value Measurement | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	32,511	31,673
Estimate of Fair Value Measurement | Commercial, financial and industrial | Level 1
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Commercial, financial and industrial | Level 2
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Commercial, financial and industrial | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	32,511	31,673
Estimate of Fair Value Measurement | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,894	13,831
Estimate of Fair Value Measurement | Commercial real estate | Level 1
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Commercial real estate | Level 2
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Commercial real estate | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	13,894	13,831
Estimate of Fair Value Measurement | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,262	12,605
Estimate of Fair Value Measurement | Consumer real estate | Level 1
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Consumer real estate | Level 2
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Consumer real estate | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	13,262	12,605
Estimate of Fair Value Measurement | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	657	742
Estimate of Fair Value Measurement | Credit card and other | Level 1
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Credit card and other | Level 2
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Credit card and other | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	657	742
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	85	68
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Level 2
Short-term financial assets:
Loans held for sale:	69	42
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | 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:	439	407
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | Level 2
Short-term financial assets:
Loans held for sale:	439	407
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM | 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 | Level 1
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans - LOCOM | Level 2
Short-term financial assets:
Loans held for sale:	0	0
Estimate of Fair Value Measurement | Mortgage loans - LOCOM | Level 3
Short-term financial assets:
Loans held for sale:	27	28
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	20,992	24,579
Standby and other commitments	$ 753	$ 746