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Pension and Other Postretirement Benefit Plans - Summary of Amounts Recognized In Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]    
Accumulated other comprehensive loss $ (135,596) $ (143,389)
Pension Benefits    
Defined Benefit Plan And Other Postretirement Benefit Plan Table Text Block [Line Items]    
Net actuarial loss (159,709) (154,608)
Prior service credit 9,099 10,210
Pension settlement 14,005 0
Accumulated other comprehensive loss $ (136,605) $ (144,398)