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Pension and Other Postretirement Benefits - Postretirement assumptions and trends (Details) - Postemployment Retirement Benefits
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Weighted average assumptions used to determine the company's obligations      
Discount rate (as a percent) 4.22% 3.69%  
Weighted average assumptions used to determine the company's net periodic benefit cost      
Discount rate (as a percent) 3.69% 4.42% 5.49%
UNITED STATES      
Assumptions used in measuring benefit obligation      
2021 increase in per capita cost (as a percent) 6.00%    
Ultimate trend (as a percent) 4.50%    
Year ultimate trend reached 2032    
CANADA      
Assumptions used in measuring benefit obligation      
2021 increase in per capita cost (as a percent) 5.74%    
Ultimate trend (as a percent) 4.00%    
Year ultimate trend reached 2040    
BRAZIL      
Assumptions used in measuring benefit obligation      
2021 increase in per capita cost (as a percent) 7.79%    
Ultimate trend (as a percent) 7.79%    
Year ultimate trend reached 2021