Annual report pursuant to Section 13 and 15(d)

Pension And Other Postretirement Benefit Programs - Expected Future Benefit Payments (Details)

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Pension And Other Postretirement Benefit Programs - Expected Future Benefit Payments (Details)
Dec. 31, 2020
USD ($)
Retiree Health and Life Insurance Plans  
Defined Benefit Plan Disclosure [Line Items]  
Expected employer contributions, next fiscal year $ 4,100,000
U.S. Pension Benefits, Canadian Pension Benefits, and Retiree Health and Life Insurance Benefits, Gross  
2019 4,100,000
2020 3,800,000
2021 3,600,000
2022 3,500,000
2023 3,400,000
2026-2030 15,700,000
Pension Plan  
Defined Benefit Plan Disclosure [Line Items]  
Expected employer contributions, next fiscal year 100,000
United States | Pension Plan  
U.S. Pension Benefits, Canadian Pension Benefits, and Retiree Health and Life Insurance Benefits, Gross  
2019 19,900,000
2020 20,900,000
2021 21,600,000
2022 21,700,000
2023 22,100,000
2026-2030 114,100,000
Canadian Pension Plan | Pension Plan  
U.S. Pension Benefits, Canadian Pension Benefits, and Retiree Health and Life Insurance Benefits, Gross  
2019 1,300,000
2020 1,300,000
2021 1,200,000
2022 1,200,000
2023 1,100,000
2026-2030 $ 5,300,000