Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Fair Value Measurement (Details)

v3.20.1
Pension And Other Postretirement Benefit Programs - Fair Value Measurement (Details) - Pension Plan - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
United States      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 380.7 $ 337.1 $ 390.8
Assets received from separation 0.0 (8.1)  
United States | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets (0.4)    
United States | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 381.1    
United States | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0    
United States | Fixed income securities      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 207.9 202.4  
United States | Fixed income securities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Fixed income securities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 207.9 202.4  
United States | Fixed income securities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Equities      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 173.2 143.2  
United States | Equities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Equities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 173.2 143.2  
United States | Equities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Other      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets (0.4) (0.4)  
United States | Other | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets (0.4) (0.4)  
United States | Other | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Other | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
United States | Plan Assets Before Transfer to AHF, LLC      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets   345.2  
United States | Plan Assets Before Transfer to AHF, LLC | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets   (0.4)  
United States | Plan Assets Before Transfer to AHF, LLC | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets   345.6  
United States | Plan Assets Before Transfer to AHF, LLC | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets   0.0  
Canadian Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 14.2 13.6 $ 17.1
Assets received from separation 0.0 0.0  
Canadian Pension Plan | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.3 0.2  
Canadian Pension Plan | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 13.9 13.4  
Canadian Pension Plan | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Fixed income securities      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7.0 6.9  
Canadian Pension Plan | Fixed income securities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Fixed income securities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 7.0 6.9  
Canadian Pension Plan | Fixed income securities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Equities      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 6.9 6.5  
Canadian Pension Plan | Equities | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Equities | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 6.9 6.5  
Canadian Pension Plan | Equities | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Other      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.3 0.2  
Canadian Pension Plan | Other | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.3 0.2  
Canadian Pension Plan | Other | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets 0.0 0.0  
Canadian Pension Plan | Other | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair Value of Plan Assets $ 0.0 $ 0.0