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Retirement Plans and Other Post-Retirement Benefits - Additional Information (Detail) $ in Millions |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Oct. 31, 2018 USD ($) | Oct. 31, 2018 USD ($) | Dec. 31, 2018 USD ($) Age | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Comprehensive medical plan for retiree employees eligible age to participate in health care benefit plan | Age |  |  | 65 |  |
Comprehensive medical plan for retiree employees eligible age for avail defray costs of Medicare | Age |  |  | 65 |  |
Accumulated benefit obligation for all defined benefit pension plans |  |  | $ 324.0 | $ 320.7 |
Defined contribution plans Employees contribution |  |  | 50.00% |  |
Expense associated with Defined Contribution Plans |  |  | $ 0.4 | 0.3 | $ 0.2
Minimum [Member] | Fixed Income, Cash and Cash Equivalents [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target allocation for the plan assets |  |  | 80.00% |  |
Maximum [Member] | Fixed Income, Cash and Cash Equivalents [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target allocation for the plan assets |  |  | 100.00% |  |
Pension Benefits [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Related assets transferred from existing pension plan |  |  | $ 25.7 | $ 27.9 |
Discount rates |  |  | 4.34% | 3.85% |
Pension settlement charge |  |  |  |  | 7.3
Pension settlement charge settled |  |  |  |  | $ 24.2
Pension Benefits [Member] | Minimum [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Discount rates |  |  | 2.05% |  |
Pension Benefits [Member] | Maximum [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Discount rates |  |  | 4.54% |  |
Other Benefits [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Discount rates |  |  | 4.19% | 3.68% |
Other Benefits [Member] | Minimum [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Discount rates |  |  | 4.11% |  |
Other Benefits [Member] | Maximum [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Discount rates |  |  | 4.22% |  |
Specialty Papers [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Pension liabilities assumed | $ 210.0 | $ 210.0 |  |  |
Retiree healthcare liabilities | 38.0 | 38.0 |  |  |
Related assets transferred from existing pension plan | $ 280.0 | $ 280.0 |  |  |

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