Retirement Plans and Other Post-Retirement Benefits - Additional Information (Detail) $ in Millions			1 Months Ended	12 Months Ended
	Jun. 01, 2019	Oct. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Age	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Employer contribution of employee’s eligible earnings, percentage	7.00%
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
Projected benefit obligation				$ 45.7	$ 42.2
Accumulated benefit obligation for all defined benefit pension plans				$ 45.7	324.0
Defined contribution plans Employees contribution				50.00%
Expense associated with Defined Contribution Plans				$ 1.9	0.4	$ 0.3
Non-qualified Plans [Member] | Unfunded [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation				45.7
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		$ 274.0	$ 274.0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Decrease in projected benefit obligation				309.5
Decrease in plan assets				309.5
Pension plan settlement charge				75.3
Assets remain in pension trust				7.7	1.0
Pension assets expected to revert				32.0
Related assets transferred from existing pension plan				$ 5.7	$ 25.7
Discount rates				2.70%	4.34%
Pension Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates				3.25%
Pension Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates				1.22%
Pension Benefits [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets remain in pension trust				$ 53.4
Pension Benefits [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets remain in pension trust				$ 53.4
Deferred Compensation Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution of employee’s eligible earnings, percentage				7.00%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets remain in pension trust				$ (6.5)	$ (9.2)
Discount rates				3.11%	4.19%
Other Benefits [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates				3.25%
Other Benefits [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates				2.93%