Fair Value of Assets and Liabilities - Schedule of Book Value And Estimated Fair Value Of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets
Total loans and leases, net of allowance for loan and lease losses	$ 60,519	$ 57,417
Short-term financial assets:
Interest-bearing deposits with banks	1,328	1,384
Securities purchased under agreements to resell	519	353
Trading securities:	1,412	1,375
Loans held-for-sale	502	590
Securities held to maturity	1,323	1,371
Derivative assets	576	458
Other assets:
Total assets	81,661	78,953
Liabilities:
Trading liabilities	509	335
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,921	1,013
Term borrowings:
Other long-term borrowings	1,150	1,597
Derivative assets	675	929
Total liabilities	72,370	70,406
Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	24	50
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	60,519	57,417
Short-term financial assets:
Interest-bearing deposits with banks	1,328	1,384
Federal funds sold	200	129
Securities purchased under agreements to resell	519	353
Total short-term financial assets	2,047	1,866
Trading securities:	1,412	1,375
Loans held-for-sale	502	590
Securities available for sale at fair value	8,391	8,836
Securities held to maturity	1,323	1,371
Derivative assets	577	460
Other assets:
Tax credit investments	665	547
Deferred compensation mutual funds	102	112
Equity, mutual funds, and other	261	275
Total other assets	1,028	934
Total assets	75,799	72,849
Liabilities:
Defined maturity	6,804	2,887
Trading liabilities	509	335
Short-term financial liabilities:
Federal funds purchased	302	400
Securities sold under agreements to repurchase	1,921	1,013
Other short-term borrowings	326	1,093
Total short-term financial liabilities	2,549	2,506
Term borrowings:
Real estate investment trust-preferred	47	46
Term borrowings—new market tax credit investment	65	66
Secured borrowings	3	3
Junior subordinated debentures	150	148
Other long-term borrowings	885	1,334
Total term borrowings	1,150	1,597
Derivative assets	699	958
Total liabilities	11,711	8,283
Reported Value Measurement | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	32,294	31,473
Reported Value Measurement | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	14,044	13,082
Reported Value Measurement | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,417	12,053
Reported Value Measurement | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	764	809
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held-for-sale	68	51
Reported Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held-for-sale	406	506
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held-for-sale	28	33
Estimate of Fair Value Measurement
Assets
Total loans and leases, net of allowance for loan and lease losses	58,868	56,982
Short-term financial assets:
Interest-bearing deposits with banks	1,328	1,384
Federal funds sold	200	129
Securities purchased under agreements to resell	519	353
Total short-term financial assets	2,047	1,866
Trading securities:	1,412	1,375
Loans held-for-sale	503	596
Securities available for sale at fair value	8,391	8,836
Securities held to maturity	1,161	1,209
Derivative assets	577	460
Other assets:
Tax credit investments	653	542
Deferred compensation mutual funds	102	112
Equity, mutual funds, and other	261	275
Total other assets	1,016	929
Total assets	73,975	72,253
Liabilities:
Defined maturity	6,851	2,890
Trading liabilities	509	335
Short-term financial liabilities:
Federal funds purchased	302	400
Securities sold under agreements to repurchase	1,921	1,013
Other short-term borrowings	326	1,093
Total short-term financial liabilities	2,549	2,506
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	60	59
Secured borrowings	3	3
Junior subordinated debentures	150	150
Other long-term borrowings	824	1,301
Total term borrowings	1,084	1,560
Derivative assets	699	958
Total liabilities	11,692	8,249
Loan commitments	1	1
Standby and other commitments	8	7
Estimate of Fair Value Measurement | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	31,678	31,329
Estimate of Fair Value Measurement | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,832	12,909
Estimate of Fair Value Measurement | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	12,616	11,934
Estimate of Fair Value Measurement | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	742	810
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held-for-sale	68	51
Estimate of Fair Value Measurement | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held-for-sale	407	512
Estimate of Fair Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held-for-sale	28	33
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	1,328	1,384
Federal funds sold	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	1,328	1,384
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	9	9
Other assets:
Tax credit investments	0	0
Deferred compensation mutual funds	102	112
Equity, mutual funds, and other	34	22
Total other assets	136	134
Total assets	1,473	1,527
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 investment	0	0
Secured borrowings	0	0
Junior subordinated debentures	0	0
Other long-term borrowings	0	0
Total term borrowings	0	0
Derivative assets	10	8
Total liabilities	10	8
Estimate of Fair Value Measurement | Level 1 | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 1 | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 1 | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 1 | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 1 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held-for-sale	0	0
Estimate of Fair Value Measurement | Level 1 | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held-for-sale	0	0
Estimate of Fair Value Measurement | Level 1 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held-for-sale	0	0
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	200	129
Securities purchased under agreements to resell	519	353
Total short-term financial assets	719	482
Trading securities:	1,399	1,350
Loans held-for-sale	449	541
Securities available for sale at fair value	8,391	8,836
Securities held to maturity	1,161	1,209
Derivative assets	568	451
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	12,687	12,869
Liabilities:
Defined maturity	6,851	2,890
Trading liabilities	509	335
Short-term financial liabilities:
Federal funds purchased	302	400
Securities sold under agreements to repurchase	1,921	1,013
Other short-term borrowings	326	1,093
Total short-term financial liabilities	2,549	2,506
Term borrowings:
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	824	1,301
Total term borrowings	824	1,301
Derivative assets	666	923
Total liabilities	11,399	7,955
Estimate of Fair Value Measurement | Level 2 | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 2 | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 2 | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 2 | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	0	0
Estimate of Fair Value Measurement | Level 2 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held-for-sale	42	29
Estimate of Fair Value Measurement | Level 2 | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held-for-sale	407	512
Estimate of Fair Value Measurement | Level 2 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held-for-sale	0	0
Estimate of Fair Value Measurement | Level 3
Assets
Total loans and leases, net of allowance for loan and lease losses	58,868	56,982
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:	13	25
Loans held-for-sale	54	55
Securities available for sale at fair value	0	0
Securities held to maturity	0	0
Derivative assets	0	0
Other assets:
Tax credit investments	653	542
Deferred compensation mutual funds	0	0
Equity, mutual funds, and other	227	253
Total other assets	880	795
Total assets	59,815	57,857
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 investment	60	59
Secured borrowings	3	3
Junior subordinated debentures	150	150
Other long-term borrowings	0	0
Total term borrowings	260	259
Derivative assets	23	27
Total liabilities	283	286
Estimate of Fair Value Measurement | Level 3 | Commercial, financial and industrial
Assets
Total loans and leases, net of allowance for loan and lease losses	31,678	31,329
Estimate of Fair Value Measurement | Level 3 | Commercial real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	13,832	12,909
Estimate of Fair Value Measurement | Level 3 | Consumer real estate
Assets
Total loans and leases, net of allowance for loan and lease losses	12,616	11,934
Estimate of Fair Value Measurement | Level 3 | Credit card and other
Assets
Total loans and leases, net of allowance for loan and lease losses	742	810
Estimate of Fair Value Measurement | Level 3 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held-for-sale	26	22
Estimate of Fair Value Measurement | Level 3 | USDA & SBA loans - LOCOM
Short-term financial assets:
Loans held-for-sale	0	0
Estimate of Fair Value Measurement | Level 3 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held-for-sale	28	33
Contractual Amount
Term borrowings:
Loan commitments	24,579	25,953
Standby and other commitments	$ 746	$ 754