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Employee Benefits, Fair Value of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | $ 70.6 | $ 68.1
Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 16.1 | 20.1
Deferred Compensation Plan Assets | 8.1 | 10.5
Fair Value, Measurements, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 8.0 | 9.6
Deferred Compensation Plan Assets | 0.0 | 0.0
Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 8.1 | 10.5
Deferred Compensation Plan Assets | 8.1 | 10.5
Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Deferred Compensation Plan Assets | 0.0 | 0.0
Salaried VEBA | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 8.0 | 9.6
Salaried VEBA | Fair Value, Measurements, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 8.0 | 9.6
Salaried VEBA | Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Salaried VEBA | Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Salaried VEBA | Diversified Investment Funds in Registered Investment Companies | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 7.1 | 8.7
Salaried VEBA | Diversified Investment Funds in Registered Investment Companies | Fair Value, Measurements, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 7.1 | 8.7
Salaried VEBA | Diversified Investment Funds in Registered Investment Companies | Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Salaried VEBA | Diversified Investment Funds in Registered Investment Companies | Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Salaried VEBA | Equity Funds | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 24.8 | 20.3
Salaried VEBA | Fixed Income Funds | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 21.9 | 21.2
Salaried VEBA | Cash and Cash Equivalents | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.9 | 0.9
Salaried VEBA | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.9 | 0.9
Salaried VEBA | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Salaried VEBA | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | 0.0 | 0.0
Canadian pension plan | Diversified Investment Funds in Registered Investment Companies | Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Defined Benefit Plan, Plan Assets, Amount | $ 7.8 | $ 6.5

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