Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Narrative (Details)

v3.20.1
Pension And Other Postretirement Benefit Programs - Narrative (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]    
Defined contribution plan costs $ 5.5 $ 6.2
Minimum    
Defined Benefit Plan Disclosure [Line Items]    
Asset class performance period 20 years  
Retiree Health and Life Insurance Plans    
Defined Benefit Plan Disclosure [Line Items]    
Health care cost trend rate assumed for next fiscal year, pre-65 retiree 7.10%  
Health care cost rate assumed 4.50%  
Expected amortization of unrecognized net actuarial losses in next fiscal year $ 2.4  
Retiree Health and Life Insurance Plans | Minimum    
Defined Benefit Plan Disclosure [Line Items]    
Health care cost trend rate assumed for next fiscal year, post-65 retiree 6.50%  
Retiree Health and Life Insurance Plans | Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Health care cost trend rate assumed for next fiscal year, post-65 retiree 8.20%  
U.S. Pension Plan | Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Expected return on plan assets (in percentage) 6.30% 5.85%
Expected unrecognized prior service cost and net actuarial losses to be recognized in next fiscal year $ 10.1  
Expected employer contributions, next fiscal year 0.1  
U.S. Pension Plan | Retiree Health and Life Insurance Plans    
Defined Benefit Plan Disclosure [Line Items]    
Expected employer contributions, next fiscal year $ 5.6  
Canadian Pension Plan | Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Expected return on plan assets (in percentage) 4.90% 4.90%
Expected unrecognized prior service cost and net actuarial losses to be recognized in next fiscal year $ 0.4  
Expected employer contributions, next fiscal year $ 0.1