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Pension Plan and Other Postretirement Benefits - Narrative (Details)
$ in Thousands
 1 Months Ended 12 Months Ended
Jan. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
year
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Defined Benefit Plan Disclosure [Line Items]        
Defined contribution plan, cost   $ 5,300 $ 5,300 $ 4,500
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Percentage vesting after the specified employment period   100.00%    
Vesting period   5 years    
Age for compensation | year   65    
Age below which compensation is reduced | year   62    
Plan assets at fair value, valuation inputs, period over which investment gains or losses are recognized   5 years    
Net Company Contribution   $ 11,200 22,500  
Investment redemption, notice period   95 days    
Funds' assets, availability period   30 days    
Pension Plan | Subsequent Event        
Defined Benefit Plan Disclosure [Line Items]        
Net Company Contribution $ 10,000      
Other Postretirement Benefits Plan        
Defined Benefit Plan Disclosure [Line Items]        
Net Company Contribution   $ 2,662 2,757  
Health insurance benefits, requisite age   55 years    
Health insurance benefits, requisite service period   10 years    
Plan Amendments   $ (3,891) $ (20,864)