Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Amounts Recognized in AOCI (Details)

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Pension And Other Postretirement Benefit Programs - Amounts Recognized in AOCI (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Retiree Health and Life Insurance Plans    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain $ 41.0 $ 34.8
U.S. Pension Plan | Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain (124.2) (127.4)
Canadian Pension Plan | Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Net actuarial gain $ (4.7) $ (3.8)