Annual report pursuant to Section 13 and 15(d)

Employee Retirement Plans - Assumptions (Details)

v3.20.4
Employee Retirement Plans - Assumptions (Details)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2015
Minimum        
Assumptions used in determining net periodic pension cost for the plans        
Discount rates (as a percent)       3.60%
Pension plan        
Assumptions used to determine the benefit obligation        
Discount rate (as a percent)     3.60%  
Salaried Pension Plan        
Assumptions used in determining net periodic pension cost for the plans        
Rates of increase in compensation levels: Salaried (as a percent)     3.50%  
Expected long-term rate of return on assets (as a percent)     5.80%  
Hourly Pension Plan        
Assumptions used in determining net periodic pension cost for the plans        
Expected long-term rate of return on assets (as a percent)     6.50%  
Assumptions used to determine the benefit obligation        
Discount rate (as a percent)     4.20%  
Other postretirement benefit cost        
Assumptions used in determining net periodic pension cost for the plans        
Discount rates (as a percent) 3.00% 4.00% 3.40%  
Summary of healthcare cost trend rates        
Ultimate healthcare cost trend rate (as a percent) 4.50% 4.50% 4.50%  
Participation (as a percent) 60.00% 60.00% 60.00%  
Assumed health care cost trend rate for the next fiscal year (as a percent) 7.00% 6.80% 6.80%  
Ultimate rate in 2029 (as a percent) 4.50%      
Ultimate rate in 2028 (as a percent)   4.50%    
Ultimate rate in 2027 (as a percent)     4.50%  
Assumptions used to determine the benefit obligation        
Discount rate (as a percent) 2.10% 3.00%