Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Assets:
Net loans and leases	$ 63,647	$ 63,418
Short-term financial assets:
Interest-bearing deposits with banks	1,116	1,125
Securities purchased under agreements to resell	746	613
Trading securities	1,812	1,904
Loans held for sale:	562	406
Securities available for sale at fair value	8,146	8,165
Securities held to maturity	1,204	1,216
Derivative assets	333	327
Other assets:
Total assets	84,132	83,876
Liabilities:
Trading liabilities	666	607
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,400	1,973
Term borrowings:
Other long-term borrowings	1,318	1,321
Derivative liabilities	395	376
Total liabilities	74,667	74,734
Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	110	41
Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	203
Reported Value Measurement
Assets:
Net loans and leases	63,647	63,418
Short-term financial assets:
Interest-bearing deposits with banks	1,116	1,125
Federal funds sold	8	21
Securities purchased under agreements to resell	746	613
Total short-term financial assets	1,870	1,759
Trading securities	1,812	1,904
Loans held for sale:	562	406
Securities available for sale at fair value	8,146	8,165
Securities held to maturity	1,204	1,216
Derivative assets	336	327
Other assets:
Tax credit investments	803	824
Deferred compensation mutual funds	106	110
Equity, mutual funds, and other	330	281
Total other assets	1,239	1,215
Total assets	78,816	78,410
Liabilities:
Defined maturity deposits	7,125	6,485
Trading liabilities	666	607
Short-term financial liabilities:
Federal funds purchased	793	1,039
Securities sold under agreements to repurchase	1,400	1,973
Other short-term borrowings	1,975	242
Total short-term financial liabilities	4,168	3,254
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—New Market Tax Credit investments	74	74
Secured borrowings	9	12
Junior subordinated debentures	153	153
Other long-term borrowings	1,035	1,035
Total term borrowings	1,318	1,321
Derivative liabilities	414	402
Total liabilities	13,691	12,069
Reported Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	36,114	35,570
Reported Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,264	13,386
Reported Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	13,727	13,902
Reported Value Measurement | Credit card and other
Assets:
Net loans and leases	542	560
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	167	151
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	373	233
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	22	22
Estimate of Fair Value Measurement
Assets:
Net loans and leases	63,133	62,955
Short-term financial assets:
Interest-bearing deposits with banks	1,116	1,125
Federal funds sold	8	21
Securities purchased under agreements to resell	746	613
Total short-term financial assets	1,870	1,759
Trading securities	1,812	1,904
Loans held for sale:	563	406
Securities available for sale at fair value	8,146	8,165
Securities held to maturity	1,056	1,073
Derivative assets	336	327
Other assets:
Tax credit investments	739	758
Deferred compensation mutual funds	106	110
Equity, mutual funds, and other	330	281
Total other assets	1,175	1,149
Total assets	78,091	77,738
Liabilities:
Defined maturity deposits	7,101	6,466
Trading liabilities	666	607
Short-term financial liabilities:
Federal funds purchased	793	1,039
Securities sold under agreements to repurchase	1,400	1,973
Other short-term borrowings	1,975	242
Total short-term financial liabilities	4,168	3,254
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—New Market Tax Credit investments	72	73
Secured borrowings	9	12
Junior subordinated debentures	150	150
Other long-term borrowings	1,040	1,058
Total term borrowings	1,318	1,340
Derivative liabilities	414	402
Total liabilities	13,667	12,069
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	9	10
Estimate of Fair Value Measurement | Level 1
Assets:
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	1,116	1,125
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,116	1,125
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	26	7
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	106	110
Equity, mutual funds, and other	17	37
Total other assets	123	147
Total assets	1,265	1,279
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
Notes payable—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	19	9
Total liabilities	19	9
Estimate of Fair Value Measurement | Level 2
Assets:
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	8	21
Securities purchased under agreements to resell	746	613
Total short-term financial assets	754	634
Trading securities	1,777	1,859
Loans held for sale:	527	370
Securities available for sale at fair value	8,146	8,165
Securities held to maturity	1,056	1,073
Derivative assets	310	320
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	12,570	12,421
Liabilities:
Defined maturity deposits	7,101	6,466
Trading liabilities	666	607
Short-term financial liabilities:
Federal funds purchased	793	1,039
Securities sold under agreements to repurchase	1,400	1,973
Other short-term borrowings	1,975	242
Total short-term financial liabilities	4,168	3,254
Term borrowings:
Real estate investment trust-preferred	0	0
Notes payable—New Market Tax Credit investments	0	0
Secured borrowings	0	0
Junior subordinated debentures	0	0
Other long-term borrowings	1,040	1,058
Total term borrowings	1,040	1,058
Derivative liabilities	377	368
Total liabilities	13,352	11,753
Estimate of Fair Value Measurement | Level 3
Assets:
Net loans and leases	63,133	62,955
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	35	45
Loans held for sale:	36	36
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	0	0
Other assets:
Tax credit investments	739	758
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	313	244
Total other assets	1,052	1,002
Total assets	64,256	64,038
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
Notes payable—New Market Tax Credit investments	72	73
Secured borrowings	9	12
Junior subordinated debentures	150	150
Other long-term borrowings	0	0
Total term borrowings	278	282
Derivative liabilities	18	25
Total liabilities	296	307
Estimate of Fair Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	35,861	35,401
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Level 3
Assets:
Net loans and leases	35,861	35,401
Estimate of Fair Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,211	13,289
Estimate of Fair Value Measurement | Commercial Real Estate | Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Level 3
Assets:
Net loans and leases	13,211	13,289
Estimate of Fair Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	13,518	13,707
Estimate of Fair Value Measurement | Consumer Real Estate | Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Level 3
Assets:
Net loans and leases	13,518	13,707
Estimate of Fair Value Measurement | Credit card and other
Assets:
Net loans and leases	543	558
Estimate of Fair Value Measurement | Credit card and other | Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Level 3
Assets:
Net loans and leases	543	558
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	167	151
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:	153	137
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Level 3
Short-term financial assets:
Loans held for sale:	14	14
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	374	233
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:	374	233
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:	22	22
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:	22	22
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	22,063	21,676
Standby and other commitments	$ 783	$ 804