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Benefit Plans - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Benefit Plans      
Employee's eligibility age to receive a defined monthly benefit 65 years    
Accrual for present value of future benefit payments $ 2.7 $ 2.8  
Expenses related to the plan 0.2 0.2 $ 0.2
Expenses related to the savings and retirement plan 2.6 2.0 0.6
Expenses for contributions not reimbursed by clients related to multiemployer defined benefit and defined contribution plans 1.0 0.9 0.8
Non-qualified deferred compensation plan      
Benefit Plans      
Cash surrender value of life insurance contracts 22.5 19.2  
Maximum annual contribution an employee is permitted to defer 0.1    
Deferred compensation liability 24.9 19.4  
Deferred benefits for certain former key executives | Central      
Benefit Plans      
Accrual for present value of future benefit payments 1.3 1.4  
Expenses related to the plan $ 0.2 0.2 $ 0.2
Minimum period over which the annual payments will be made when the executives retire or upon death or disability 10 years    
Face value of life insurance contracts $ 4.1 4.1  
Cash surrender value of life insurance contracts $ 3.4 $ 3.3  
Savings and Retirement 401K Plan      
Benefit Plans      
Employer match of first tier of employee contributions (in percentage) 50.00%    
First tier percentage of compensation eligible for match by employer 6.00%