Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Assets:
Net loans and leases	$ 62,446	$ 61,750
Short-term financial assets:
Interest-bearing deposits with banks	911	1,538
Securities purchased under agreements to resell	493	572
Trading securities	1,430	1,387
Loans held for sale:	402	551
Securities available for sale at fair value	8,117	7,896
Securities held to maturity	1,245	1,270
Derivative assets	383	530
Other assets:
Total assets	82,084	82,152
Liabilities:
Trading liabilities	469	550
Short-term financial liabilities:
Securities sold under agreements to repurchase	2,205	2,096
Term borrowings:
Other long-term borrowings	1,342	1,195
Derivative liabilities	440	655
Total liabilities	72,827	73,041
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	83	51
Fair Value, Inputs, Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	203
Reported Value Measurement
Assets:
Net loans and leases	62,446	61,750
Short-term financial assets:
Interest-bearing deposits with banks	911	1,538
Federal funds sold	34	59
Securities purchased under agreements to resell	493	572
Total short-term financial assets	1,438	2,169
Trading securities	1,430	1,387
Loans held for sale:	402	551
Securities available for sale at fair value	8,117	7,896
Securities held to maturity	1,245	1,270
Derivative assets	383	531
Other assets:
Tax credit investments	784	706
Deferred compensation mutual funds	111	111
Equity, mutual funds, and other	322	289
Total other assets	1,217	1,106
Total assets	76,678	76,660
Liabilities:
Defined maturity deposits	7,270	6,613
Trading liabilities	469	550
Short-term financial liabilities:
Federal funds purchased	996	259
Securities sold under agreements to repurchase	2,205	2,096
Other short-term borrowings	260	1,045
Total short-term financial liabilities	3,461	3,400
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—new market tax credit investments	74	74
Secured borrowings	34	37
Junior subordinated debentures	152	151
Other long-term borrowings	1,035	886
Total term borrowings	1,342	1,195
Derivative liabilities	455	671
Total liabilities	12,997	12,429
Reported Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	34,012	33,083
Reported Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,723	14,194
Reported Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	14,135	13,826
Reported Value Measurement | Credit card and other
Assets:
Net loans and leases	576	647
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	114	85
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	264	439
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale:	24	27
Estimate of Fair Value Measurement
Assets:
Net loans and leases	61,405	60,324
Short-term financial assets:
Interest-bearing deposits with banks	911	1,538
Federal funds sold	34	59
Securities purchased under agreements to resell	493	572
Total short-term financial assets	1,438	2,169
Trading securities	1,430	1,387
Loans held for sale:	403	551
Securities available for sale at fair value	8,117	7,896
Securities held to maturity	1,083	1,083
Derivative assets	383	531
Other assets:
Tax credit investments	733	692
Deferred compensation mutual funds	111	111
Equity, mutual funds, and other	322	289
Total other assets	1,166	1,092
Total assets	75,425	75,033
Liabilities:
Defined maturity deposits	7,246	6,591
Trading liabilities	469	550
Short-term financial liabilities:
Federal funds purchased	996	259
Securities sold under agreements to repurchase	2,205	2,096
Other short-term borrowings	260	1,045
Total short-term financial liabilities	3,461	3,400
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—new market tax credit investments	72	70
Secured borrowings	34	37
Junior subordinated debentures	142	142
Other long-term borrowings	1,039	866
Total term borrowings	1,334	1,162
Derivative liabilities	455	671
Total liabilities	12,965	12,374
Unfunded Commitments [Abstract]
Loan commitments	1	1
Standby and other commitments	9	9
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Assets:
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	911	1,538
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	911	1,538
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	10	8
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	111	111
Equity, mutual funds, and other	36	35
Total other assets	147	146
Total assets	1,068	1,692
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	12	6
Total liabilities	12	6
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Assets:
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold	34	59
Securities purchased under agreements to resell	493	572
Total short-term financial assets	527	631
Trading securities	1,403	1,364
Loans held for sale:	367	508
Securities available for sale at fair value	8,117	7,896
Securities held to maturity	1,083	1,083
Derivative assets	373	523
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	11,870	12,005
Liabilities:
Defined maturity deposits	7,246	6,591
Trading liabilities	469	550
Short-term financial liabilities:
Federal funds purchased	996	259
Securities sold under agreements to repurchase	2,205	2,096
Other short-term borrowings	260	1,045
Total short-term financial liabilities	3,461	3,400
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	1,039	866
Total term borrowings	1,039	866
Derivative liabilities	430	650
Total liabilities	12,645	12,057
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	61,405	60,324
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	27	23
Loans held for sale:	36	43
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	0	0
Other assets:
Tax credit investments	733	692
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	286	254
Total other assets	1,019	946
Total assets	62,487	61,336
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	70
Secured borrowings	34	37
Junior subordinated debentures	142	142
Other long-term borrowings	0	0
Total term borrowings	295	296
Derivative liabilities	13	15
Total liabilities	308	311
Estimate of Fair Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	33,574	32,511
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Fair Value, Inputs, Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Fair Value, Inputs, Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial, financial, and industrial | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	33,574	32,511
Estimate of Fair Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,636	13,894
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Commercial Real Estate | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	13,636	13,894
Estimate of Fair Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	13,600	13,262
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Consumer Real Estate | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	13,600	13,262
Estimate of Fair Value Measurement | Credit card and other
Assets:
Net loans and leases	595	657
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 1
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 2
Assets:
Net loans and leases	0	0
Estimate of Fair Value Measurement | Credit card and other | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	595	657
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale:	114	85
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	69
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	12	16
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	265	439
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:	265	439
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:	24	27
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:	24	27
Contractual Amount
Unfunded Commitments [Abstract]
Loan commitments	20,937	20,992
Standby and other commitments	$ 720	$ 753