Fair Value of Assets and Liabilities - Summary Of Book Value And Estimated Fair Value Of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	$ 55,872	$ 57,269
Short-term financial assets:
Interest-bearing deposits with banks	13,451	8,351
Securities purchased under agreements to resell	571	380
Trading securities	1,035	1,176
Loans held for sale	977	1,022
Securities available for sale at fair value	8,388	8,047
Derivative assets	479	765
Other assets:
Total assets	87,908	84,209
Liabilities:
Trading Liabilities	531	353
Short-term financial liabilities:
Securities sold under agreements to repurchase	1,350	1,187
Term borrowings:
Other long term borrowings	1,672	1,670
Gross amounts of recognized liabilities	98	125
Total liabilities	79,343	75,902
Fair Value, Inputs, Level 3 | FHLB-Cincinnati Stock
Term borrowings:
Restricted investments	32	61
Fair Value, Inputs, Level 3 | FRB Stock
Term borrowings:
Restricted investments	203	202
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	55,872	57,269
Short-term financial assets:
Interest-bearing deposits with banks	13,451	8,351
Federal funds sold and securities purchased under agreements to resell	51	65
Securities purchased under agreements to resell	571	380
Total short-term financial assets	14,073	8,796
Trading securities	1,035	1,176
Loans held for sale	973	1,022
Securities available for sale at fair value	8,388	8,047
Derivative assets	480	769
Other assets:
Tax credit investments	419	400
Deferred compensation assets	122	118
Equity, mutual funds, and other	264	288
Total other assets	805	806
Total assets	81,626	77,885
Liabilities:
Defined maturity	4,304	5,070
Trading Liabilities	531	353
Short-term financial liabilities:
Federal funds purchased	777	845
Securities sold under agreements to repurchase	1,350	1,187
Other short-term borrowings	119	166
Short Term Financial Liabilities	2,246	2,198
Term borrowings:
Real estate investment trust-preferred	46	46
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	240	238
Other long term borrowings	1,326	1,326
Total term borrowings	1,672	1,670
Gross amounts of recognized liabilities		149
Total liabilities	8,871	9,440
Reported Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	32,143	32,651
Reported Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	12,082	12,033
Reported Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	10,662	11,483
Reported Value Measurement | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	985	1,102
Reported Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	377	405
Reported Value Measurement | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	533	509
Reported Value Measurement | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Reported Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	59	77
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	56,242	57,695
Short-term financial assets:
Interest-bearing deposits with banks	13,451	8,351
Federal funds sold and securities purchased under agreements to resell	51	65
Securities purchased under agreements to resell	571	380
Total short-term financial assets	14,073	8,796
Trading securities	1,035	1,176
Loans held for sale	976	1,025
Securities available for sale at fair value	8,388	8,047
Derivative assets	480	769
Other assets:
Tax credit investments	404	371
Deferred compensation assets	122	118
Equity, mutual funds, and other	264	288
Total other assets	790	777
Total assets	81,984	78,285
Liabilities:
Defined maturity	4,311	5,083
Trading Liabilities	531	353
Short-term financial liabilities:
Federal funds purchased	777	845
Securities sold under agreements to repurchase	1,350	1,187
Other short-term borrowings	119	166
Short Term Financial Liabilities	2,246	2,198
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	237	223
Other long term borrowings	1,476	1,455
Total term borrowings	1,820	1,785
Gross amounts of recognized liabilities	118	149
Total liabilities	9,026	9,568
Unfunded Commitments:
Loan commitments	1	2
Standby and other commitments	8	6
Estimate of Fair Value Measurement | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	31,935	32,582
Estimate of Fair Value Measurement | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	12,108	12,079
Estimate of Fair Value Measurement | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	11,190	11,903
Estimate of Fair Value Measurement | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	1,009	1,131
Estimate of Fair Value Measurement | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	377	405
Estimate of Fair Value Measurement | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	536	512
Estimate of Fair Value Measurement | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Estimate of Fair Value Measurement | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	59	77
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	13,451	8,351
Federal funds sold and securities purchased under agreements to resell	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	13,451	8,351
Trading securities	0	0
Loans held for sale	0	0
Securities available for sale at fair value	0	0
Derivative assets	27	63
Other assets:
Tax credit investments	0	0
Deferred compensation assets	122	118
Equity, mutual funds, and other	29	25
Total other assets	151	143
Total assets	13,629	8,557
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
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
Gross amounts of recognized liabilities	26	71
Total liabilities	26	71
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold and securities purchased under agreements to resell	51	65
Securities purchased under agreements to resell	571	380
Total short-term financial assets	622	445
Trading securities	1,035	1,176
Loans held for sale	891	935
Securities available for sale at fair value	8,358	8,015
Derivative assets	453	706
Other assets:
Tax credit investments	0	0
Deferred compensation assets	0	0
Equity, mutual funds, and other	0	0
Total other assets	0	0
Total assets	11,359	11,277
Liabilities:
Defined maturity	4,311	5,083
Trading Liabilities	531	353
Short-term financial liabilities:
Federal funds purchased	777	845
Securities sold under agreements to repurchase	1,350	1,187
Other short-term borrowings	119	166
Short Term Financial Liabilities	2,246	2,198
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	1,476	1,455
Total term borrowings	1,476	1,455
Gross amounts of recognized liabilities	74	64
Total liabilities	8,638	9,153
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	352	393
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	535	511
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	4	31
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	56,242	57,695
Short-term financial assets:
Interest-bearing deposits with banks	0	0
Federal funds sold and securities purchased under agreements to resell	0	0
Securities purchased under agreements to resell	0	0
Total short-term financial assets	0	0
Trading securities	0	0
Loans held for sale	85	90
Securities available for sale at fair value	30	32
Derivative assets	0	0
Other assets:
Tax credit investments	404	371
Deferred compensation assets	0	0
Equity, mutual funds, and other	235	263
Total other assets	639	634
Total assets	56,996	58,451
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
Short Term Financial Liabilities	0	0
Term borrowings:
Real estate investment trust-preferred	47	47
Term borrowings—new market tax credit investment	45	45
Secured borrowings	15	15
Junior subordinated debentures	237	223
Other long term borrowings	0	0
Total term borrowings	344	330
Gross amounts of recognized liabilities	18	14
Total liabilities	362	344
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial, financial and industrial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	31,935	32,582
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	12,108	12,079
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Consumer Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	11,190	11,903
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Credit Card and Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net loans and leases	1,009	1,131
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans (elected fair value)
Short-term financial assets:
Loans held for sale	25	12
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Government guaranteed loans (SBA and USDA)
Short-term financial assets:
Loans held for sale	1	1
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Other consumer loans- LOCOM
Short-term financial assets:
Loans held for sale	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | Mortgage loans - LOCOM
Short-term financial assets:
Loans held for sale	59	77
Contractual Amount
Unfunded Commitments:
Loan commitments	22,497	20,796
Standby and other commitments	$ 789	$ 751