Segment Information - Schedule of Financial and Other Information by Business Unit (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) T	Jun. 30, 2017 USD ($) T	Jun. 30, 2018 USD ($) T	Jun. 30, 2017 USD ($) T
Segment Reporting Information [Line Items]
Total revenues	$ 406,717	$ 388,323	$ 818,792	$ 780,165
Costs of products sold	385,114	358,588	748,283	694,801
Gross profit (loss)	21,603	29,735	70,509	85,364
SG&A	31,561	31,545	68,624	66,422
(Gains) losses on dispositions of plant, equipment and timberlands, net	(579)	(58)	(2,133)	(26)
Operating income (loss)	(9,379)	(1,752)	4,018	18,968
Non-operating expense	(6,045)	(4,333)	(10,957)	(7,416)
Income (loss) before income taxes	$ (15,424)	$ (6,085)	$ (6,939)	$ 11,552
Supplementary Data
Net tons sold | T	240,600	251,500	495,400	512,400
Depreciation, depletion and amortization	$ 20,100	$ 17,700	$ 39,511	$ 34,967
Capital expenditures	10,400	34,300	36,900	71,000
Product [Member]
Segment Reporting Information [Line Items]
Total revenues	405,773	387,342	816,420	778,055
Energy and Related Sales Net [Member]
Segment Reporting Information [Line Items]
Total revenues	944	981	2,372	2,110
Composite Fibers [Member]
Segment Reporting Information [Line Items]
Total revenues	142,934	133,137	284,531	258,241
Costs of products sold	118,000	107,600	232,700	207,200
Gross profit (loss)	24,900	25,500	51,800	51,000
SG&A	11,700	10,800	23,300	21,900
Operating income (loss)	13,200	14,700	28,500	29,100
Income (loss) before income taxes	$ 13,200	$ 14,700	$ 28,500	$ 29,100
Supplementary Data
Net tons sold | T	40,400	41,900	80,500	80,700
Depreciation, depletion and amortization	$ 7,200	$ 7,000	$ 14,600	$ 13,800
Capital expenditures	2,800	2,100	7,900	6,800
Composite Fibers [Member] | Product [Member]
Segment Reporting Information [Line Items]
Total revenues	142,900	133,100	284,500	258,200
Advanced Airlaid Materials [Member]
Segment Reporting Information [Line Items]
Total revenues	72,808	62,836	142,420	122,674
Costs of products sold	62,800	53,000	122,500	103,500
Gross profit (loss)	10,000	9,800	19,900	19,200
SG&A	2,400	2,300	5,100	4,600
Operating income (loss)	7,600	7,500	14,800	14,600
Income (loss) before income taxes	$ 7,600	$ 7,500	$ 14,800	$ 14,600
Supplementary Data
Net tons sold | T	27,000	25,500	53,300	50,300
Depreciation, depletion and amortization	$ 3,500	$ 2,300	$ 6,300	$ 4,600
Capital expenditures	2,500	12,900	15,600	23,500
Advanced Airlaid Materials [Member] | Product [Member]
Segment Reporting Information [Line Items]
Total revenues	72,800	62,800	142,400	122,700
Specialty Papers [Member]
Segment Reporting Information [Line Items]
Total revenues	190,900	192,400	391,900	399,200
Costs of products sold	200,600	195,600	387,100	375,600
Gross profit (loss)	(9,700)	(3,200)	4,800	23,600
SG&A	11,200	10,300	23,300	$ 23,600
Operating income (loss)	(20,900)	(13,500)	(18,500)
Income (loss) before income taxes	$ (20,900)	$ (13,500)	$ (18,500)
Supplementary Data
Net tons sold | T	173,200	184,100	361,600	381,400
Depreciation, depletion and amortization	$ 8,200	$ 7,700	$ 16,300	$ 14,900
Capital expenditures	4,500	15,800	11,000	34,000
Specialty Papers [Member] | Product [Member]
Segment Reporting Information [Line Items]
Total revenues	190,031	191,368	389,469	397,140
Specialty Papers [Member] | Energy and Related Sales Net [Member]
Segment Reporting Information [Line Items]
Total revenues	900	1,000	2,400	2,100
Other and Unallocated [Member]
Segment Reporting Information [Line Items]
Costs of products sold	3,700	2,400	6,000	8,500
Gross profit (loss)	(3,700)	(2,400)	(6,000)	(8,500)
SG&A	6,300	8,100	16,900	16,300
(Gains) losses on dispositions of plant, equipment and timberlands, net	(600)		(2,100)
Operating income (loss)	(9,400)	(10,500)	(20,800)	(24,700)
Non-operating expense	(6,000)	(4,300)	(11,000)	(7,400)
Income (loss) before income taxes	(15,400)	(14,800)	(31,800)	(32,100)
Supplementary Data
Depreciation, depletion and amortization	1,200	700	2,300	1,700
Capital expenditures	$ 600	$ 3,500	$ 2,400	$ 6,700