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Employee Benefits - Benefit Obligations and Funded Status of Canadian Pension and Salaried VEBAs (Parenthetical) (Details) - Salaried VEBA - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |
Actuarial loss due to change in discount rate | $ 5.7 | $ 6.8
Actuarial loss due to changes in census data | $ (1.0) | 0.1
Actuarial gain due to change in the projected utilization rate |  | $ (0.5)

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- Definition Actuarial (gain) loss due to change in discount rate + References No definition available. + Details
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- Definition Actuarial (gain) loss due to change in projected utilization rate. + References No definition available. + Details
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- Definition Actuarial (gain) loss due to changes in census and mortality data + References No definition available. + Details
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- Details
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