Fair Value of Assets and Liabilities - Schedule of Book Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Assets:
Net loans and leases	$ 61,393	$ 61,750
Short-term financial assets:
Interest-bearing deposits with banks	1,164	1,538
Securities purchased under agreements to resell	681	572
Trading securities	1,376	1,387
Loans held for sale:	510	551
Securities available for sale at fair value	8,075	7,896
Securities held to maturity	1,258	1,270
Derivative assets	428	530
Other assets:
Total assets	81,491	82,152
Liabilities:
Trading liabilities	670	550
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,760	2,096
Term borrowings:
Other long-term borrowings	1,691	1,195
Derivative liabilities	510	655
Total liabilities	72,447	73,041
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	66	51
Fair Value, Inputs, Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	203
Reported Value Measurement
Assets:
Net loans and leases	61,393	61,750
Short-term financial assets:
Interest-bearing deposits with banks	1,164	1,538
Federal funds sold	47	59
Securities purchased under agreements to resell	681	572
Total short-term financial assets	1,892	2,169
Trading securities	1,376	1,387
Loans held for sale:	510	551
Securities available for sale at fair value	8,075	7,896
Securities held to maturity	1,258	1,270
Derivative assets	429	531
Other assets:
Tax credit investments	747	706
Deferred compensation mutual funds	107	111
Equity, mutual funds, and other	304	289
Total other assets	1,158	1,106
Total assets	76,091	76,660
Liabilities:
Defined maturity deposits	5,918	6,613
Trading liabilities	670	550
Short-term financial liabilities:
Federal funds purchased	812	259
Securities sold under agreements to repurchase	1,760	2,096
Other short-term borrowings	1,223	1,045
Total short-term financial liabilities	3,795	3,400
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—new market tax credit investments	74	74
Secured borrowings	35	37
Junior subordinated debentures	152	151
Other long-term borrowings	1,383	886
Total term borrowings	1,691	1,195
Derivative liabilities	529	671
Total liabilities	12,603	12,429
Reported Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	33,009	33,083
Reported Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,914	14,194
Reported Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	13,859	13,826
Reported Value Measurement | Credit card and other
Assets:
Net loans and leases	611	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:	372	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	60,157	60,324
Short-term financial assets:
Interest-bearing deposits with banks	1,164	1,538
Federal funds sold	47	59
Securities purchased under agreements to resell	681	572
Total short-term financial assets	1,892	2,169
Trading securities	1,376	1,387
Loans held for sale:	510	551
Securities available for sale at fair value	8,075	7,896
Securities held to maturity	1,092	1,083
Derivative assets	429	531
Other assets:
Tax credit investments	715	692
Deferred compensation mutual funds	107	111
Equity, mutual funds, and other	304	289
Total other assets	1,126	1,092
Total assets	74,657	75,033
Liabilities:
Defined maturity deposits	5,896	6,591
Trading liabilities	670	550
Short-term financial liabilities:
Federal funds purchased	812	259
Securities sold under agreements to repurchase	1,760	2,096
Other short-term borrowings	1,223	1,045
Total short-term financial liabilities	3,795	3,400
Term borrowings:
Real estate investment trust-preferred	47	47
Notes payable—new market tax credit investments	71	70
Secured borrowings	35	37
Junior subordinated debentures	142	142
Other long-term borrowings	1,376	866
Total term borrowings	1,671	1,162
Derivative liabilities	529	671
Total liabilities	12,561	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	1,164	1,538
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,164	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	5	8
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	107	111
Equity, mutual funds, and other	35	35
Total other assets	142	146
Total assets	1,311	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	4	6
Total liabilities	4	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	47	59
Securities purchased under agreements to resell	681	572
Total short-term financial assets	728	631
Trading securities	1,354	1,364
Loans held for sale:	473	508
Securities available for sale at fair value	8,075	7,896
Securities held to maturity	1,092	1,083
Derivative assets	424	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	12,146	12,005
Liabilities:
Defined maturity deposits	5,896	6,591
Trading liabilities	670	550
Short-term financial liabilities:
Federal funds purchased	812	259
Securities sold under agreements to repurchase	1,760	2,096
Other short-term borrowings	1,223	1,045
Total short-term financial liabilities	3,795	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	1,376	866
Total term borrowings	1,376	866
Derivative liabilities	507	650
Total liabilities	12,244	12,057
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Assets:
Net loans and leases	60,157	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	22	23
Loans held for sale:	37	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	715	692
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	269	254
Total other assets	984	946
Total assets	61,200	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	71	70
Secured borrowings	35	37
Junior subordinated debentures	142	142
Other long-term borrowings	0	0
Total term borrowings	295	296
Derivative liabilities	18	15
Total liabilities	313	311
Estimate of Fair Value Measurement | Commercial, financial, and industrial
Assets:
Net loans and leases	32,468	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	32,468	32,511
Estimate of Fair Value Measurement | Commercial Real Estate
Assets:
Net loans and leases	13,665	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	13,665	13,894
Estimate of Fair Value Measurement | Consumer Real Estate
Assets:
Net loans and leases	13,398	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	13,398	13,262
Estimate of Fair Value Measurement | Credit card and other
Assets:
Net loans and leases	626	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	626	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:	101	69
Estimate of Fair Value Measurement | Mortgage loans (elected fair value) | Fair Value, Inputs, Level 3
Short-term financial assets:
Loans held for sale:	13	16
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held for sale:	372	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:	372	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	21,158	20,992
Standby and other commitments	$ 709	$ 753