Fair Value Measurements - Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring and Non-Recurring Basis (Details) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets	$ 19.2	$ 18.7
Deferred compensation plan liabilities	19.2	18.7
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0.5	6.9
Deferred compensation plan assets	19.2	18.7
Deferred compensation plan liabilities	19.2	18.7
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0.0	5.5
Deferred compensation plan assets	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Loans And Leases Receivable, Other Real Estate Owned [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	0.0	0.0
Loans And Leases Receivable, Other Real Estate Owned [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	0.0	0.0
Loans And Leases Receivable, Other Real Estate Owned [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	16.5	12.7
US Treasury Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
US Treasury Securities [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	224.7	642.7
US Treasury Securities [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
State, county and municipal securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
State, county and municipal securities | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	219.8	263.7
State, county and municipal securities | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
US Government Agencies Debt Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
US Government Agencies Debt Securities [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	168.5	198.9
US Government Agencies Debt Securities [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	210.4	228.0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Corporate securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Corporate securities | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	236.4	241.5
Corporate securities | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Collateralized Loan Obligations | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Collateralized Loan Obligations | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,119.7	1,111.6
Collateralized Loan Obligations | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Commercial Mortgage Backed Securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Commercial Mortgage Backed Securities | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,105.6	1,351.2
Commercial Mortgage Backed Securities | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Residential Mortgage-Backed Securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Residential Mortgage-Backed Securities | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,366.9	1,558.3
Residential Mortgage-Backed Securities | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Collateralized Mortgage Obligations | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Collateralized Mortgage Obligations | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,189.5	1,350.2
Collateralized Mortgage Obligations | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	5,841.5	6,946.1
Deferred compensation plan assets	19.2	18.7
Deferred compensation plan liabilities	19.2	18.7
Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0.5	12.4
Deferred compensation plan assets	19.2	18.7
Deferred compensation plan liabilities	19.2	18.7
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	5,841.5	6,946.1
Deferred compensation plan assets	19.2	18.7
Deferred compensation plan liabilities	19.2	18.7
Estimated Fair Value | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Deferred compensation plan liabilities	0.0	0.0
Estimated Fair Value | Loans And Leases Receivable, Other Real Estate Owned [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	16.5	12.7
Estimated Fair Value | US Treasury Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	224.7	642.7
Estimated Fair Value | State, county and municipal securities | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	219.8	263.7
Estimated Fair Value | US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	168.5	198.9
Estimated Fair Value | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	210.4	228.0
Estimated Fair Value | Corporate securities | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	236.4	241.5
Estimated Fair Value | Collateralized Loan Obligations | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,119.7	1,111.6
Estimated Fair Value | Commercial Mortgage Backed Securities | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,105.6	1,351.2
Estimated Fair Value | Residential Mortgage-Backed Securities | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,366.9	1,558.3
Estimated Fair Value | Collateralized Mortgage Obligations | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,189.5	1,350.2
Interest Rate Swap | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Swap | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	37.3	45.1
Derivative liabilities	123.5	154.2
Interest Rate Swap | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.0
Derivative liabilities	0.0	0.0
Interest Rate Swap | Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	37.3	45.1
Derivative liabilities	123.5	154.2
Interest Rate Lock Commitments [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0
Interest Rate Lock Commitments [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.1
Interest Rate Lock Commitments [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0
Interest Rate Lock Commitments [Member] | Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.1
Forward Contracts [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.0
Derivative liabilities	0.0
Forward Contracts [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.1
Derivative liabilities	0.1
Forward Contracts [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.0
Derivative liabilities	0.0
Forward Contracts [Member] | Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.1
Derivative liabilities	0.1
Interest Rate Collars | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.0	0.0
Interest Rate Collars | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	3.6	5.4
Interest Rate Collars | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.0	0.0
Interest Rate Collars | Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	3.6	$ 5.4
Risk Participation Agreements | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.0
Risk Participation Agreements | Significant Other Observable Inputs (Level 2) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.1
Risk Participation Agreements | Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.0
Risk Participation Agreements | Estimated Fair Value | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 0.1
Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member] | Loans And Leases Receivable, Impaired Loans [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	1	0.45
Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Maximum [Member] | Loans And Leases Receivable, Other Real Estate Owned [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	0.43	0.36
Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Weighted Average [Member] | Loans And Leases Receivable, Impaired Loans [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	(0.36)	(0.07)
Valuation, Market Approach [Member] | Measurement Input, Discount Rate [Member] | Weighted Average [Member] | Loans And Leases Receivable, Other Real Estate Owned [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset, Measurement Input	(0.48)	(0.22)