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Defined Benefit Pension Plans - Additional Information (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]        
Net periodic benefit cost, non-service cost $ (901,000) $ (230,000) $ (2,675,000) $ (721,000)
U.S.        
Defined Benefit Plan Disclosure [Line Items]        
Contributions by employer     9,000,000 3,000,000
U.K. Plan        
Defined Benefit Plan Disclosure [Line Items]        
Contributions by employer     $ 526,000 $ 455,000