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Postretirement Benefits Other Than Pensions - Narrative (Details)
$ in Millions
 9 Months Ended 12 Months Ended
Sep. 30, 2020
Dec. 31, 2021
USD ($)
employees
Dec. 31, 2016
USD ($)
Dec. 31, 2020
USD ($)
Other Postretirement Benefit Plan, Defined Benefit        
Defined Benefit Plan Disclosure [Line Items]        
Number of retired employees covered | employees   400    
Number of active employees covered | employees   500    
Pre-tax reduction to its accumulated postretirement benefit obligation     $ 11.0  
Amounts that will be amortized from AOCI in next fiscal Year       $ 2.9
Estimated future employer contributions in next fiscal year   $ 1.2    
Medical Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Health care cost trend rate assumed for next fiscal year   6.29%   6.50%
Health care cost trend rate assumed for future years   4.80%    
Prescription Drug Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Health care cost trend rate assumed for next fiscal year   7.04%   7.50%
Health care cost trend rate assumed for future years 4.80% 4.80%