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Pension Benefits - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]    
Period of service to become eligible 6 months  
Defined Benefit Plan, Accumulated Benefit Obligation $ 3.7 $ 2.9
Subsidiaries [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Pension expense $ 0.8 $ 0.3