Nature of Operations and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended		22 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Oct. 27, 2017	Jun. 30, 2017	Dec. 15, 2015
Nature of Operations
Business Combination, Consideration Transferred				$ 71,700
Restricted Cash and Cash Equivalents, Current		$ 0		0	$ 0		$ 0
Restricted Cash and Cash Equivalents, Noncurrent		0		0	0		0
Allowance for doubtful accounts		1,300		1,500	1,300		1,300
Accumulated depreciation		1,617,500		$ 1,582,000	1,617,500		1,617,500
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 29,800			$ 29,800		$ 29,800
Percentage Of Expected Natural Gas Requirement Covered Under Contract		30.00%			30.00%		30.00%
Interest Costs Capitalized					$ 3,000	$ 1,600
Shelby paper machine interest cost capitalized					500
Entity Common Stock, Shares Outstanding								16,433,415
Land									$ 4,200
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down	$ 3,000	$ 4,300
Other Nonrecurring Expense, Planned Permaent Facility Closure		$ 800			$ 6,800
Treasury Stock, Shares		7,821,005			7,821,005		7,821,005
Common Stock
Nature of Operations
Common stock repurchase authorized										$ 100,000
Number of shares repurchased (in shares)			84,750				1,440,696
Treasury Stock Acquired, Average Cost Per Share					$ 57.53