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Employee Benefits, Defined Benefit Plans Narrative (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Accrued Annual VEBA Contribution | $ 2.9 | $ 2.1 |
Defined Benefit Plan, Plan Assets, Amount | 70.6 | 68.1 |
Union VEBA |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Accrued Annual VEBA Contribution |  | 12.8 |
Salaried VEBA |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Accrued Annual VEBA Contribution | 2.9 | 2.1 |
VEBAs |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Benefit Obligation | 90.2 | 85.6 | $ 90.0
Defined Benefit Plan, Plan Assets, Amount | 57.6 | 53.2 | 58.1
Salaried and certain hourly employee | Canadian pension plan | Maximum |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Estimated annual contribution to pension and other postretirement benefit plans | 2.9 |  |
Canadian pension plan | Canadian pension plan |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Benefit Obligation | 8.8 | 7.3 | 8.5
Defined Benefit Plan, Plan Assets, Amount | 7.8 | 6.5 | $ 7.3
Defined Benefit Plan, Accumulated Benefit Obligation | 7.6 | $ 6.4 |
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year | $ 0.5 |  |
Canadian pension plan | Canadian pension plan | Fixed Income Securities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage | 36.00% |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 35.00% |  |
Canadian pension plan | Canadian pension plan | Equity Securities |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage | 62.00% |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 60.00% |  |
Canadian pension plan | Canadian pension plan | Short-term Investments [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage | 2.00% |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 5.00% |  |

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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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