Commitments, Contingencies and Legal Proceedings - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) Operable_Unit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jul. 13, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments Contingencies And Litigation [Line Items]
Number of operable units | Operable_Unit	5
Term of agreement wih third party for monitoring and maintenance in OU1-OU4a	30 years
Assumption of escrow	$ 4,746,000
Reserve for Environmental liabilities, current portion	26,000,000				$ 26,000,000	$ 28,500,000
Other Long-Term Liabilities [Member]
Commitments Contingencies And Litigation [Line Items]
Reserve for Environmental liabilities, remaining portion					$ 19,200,000
NCR/Appvion Consent Decree [Member]
Commitments Contingencies And Litigation [Line Items]
Contribution payment towards remedial action and natural resource damages	75,000,000
Anticipated cost to complete work for remaining site remedy	200,000,000
Expected payments for governments unreimbursed past costs which are under dispute			$ 32,700,000
Unreimbursed recoverable cost			0
Unspent settlement money			4,600,000
NADAR [Member]
Commitments Contingencies And Litigation [Line Items]
Expected payments for governments unreimbursed past costs which are under dispute	105,000,000
Unspent settlement money	60,000,000
NADAR [Member] | Subsequent Event [Member]
Commitments Contingencies And Litigation [Line Items]
Expected payments for governments unreimbursed past costs which are under dispute				$ 105,000,000
Georgia Pacific [Member]
Commitments Contingencies And Litigation [Line Items]
Settlement payable amount	$ 9,500,000
Payment due date	2017-08
Maximum [Member]
Commitments Contingencies And Litigation [Line Items]
NCR costs and damages percentage	100.00%
Maximum [Member] | NCR/Appvion Consent Decree [Member]
Commitments Contingencies And Litigation [Line Items]
Estimated cost related to Fox River matter	$ 30,000,000
Minimum [Member] | December 2009 - Long Term Monitoring Plan [Member]
Commitments Contingencies And Litigation [Line Items]
Period over which cash expenditure to be incurred for monitoring activities	30 years
Minimum [Member] | GLT, GP and NCR [Member] | NCR/Appvion Consent Decree [Member]
Commitments Contingencies And Litigation [Line Items]
Contribution payment towards remedial action and natural resource damages	$ 1,000,000,000
OU2-5 [Member]
Commitments Contingencies And Litigation [Line Items]
Estimated future cost of cleanup work		$ 13,400,000	$ 13,400,000
Expected cleanup work continuation year	through 2019
NCR costs and damages percentage	100.00%
OU2-5 [Member] | Whiting Litigation [Member]
Commitments Contingencies And Litigation [Line Items]
NCR costs and damages percentage	100.00%