Consolidated Statements of Income (Loss) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 916,498	$ 927,673	$ 866,286
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs of products sold	$ 768,629	$ 780,131	$ 735,879
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 147,869	$ 147,542	$ 130,407
Selling, general and administrative expenses	100,045	94,967	111,721
Gains on dispositions of plant, equipment and timberlands, net	(1,332)	(2,060)	(3,256)
Operating income	49,156	54,635	21,942
Non-operating income (expense)
Interest expense	(7,022)	(10,408)	(15,609)
Interest income	399	1,123	559
Pension settlement	(6,154)	(75,326)
Other, net	(4,020)	(4,477)	383
Total non-operating expense	(16,797)	(89,088)	(14,667)
Income (loss) before income taxes	32,359	(34,453)	7,275
Income tax provision (benefit)	11,576	(9,242)	7,723
Income (loss) from continuing operations	20,783	(25,211)	(448)
Discontinued operations:
Income (loss) before income taxes	544	1,284	(207,242)
Income tax provision (benefit)	29	(2,386)	(30,086)
Income (loss) from discontinued operations	515	3,670	(177,156)
Net income (loss)	$ 21,298	$ (21,541)	$ (177,604)
Basic earnings (loss) per share
Income (loss) from continuing operations	$ 0.47	$ (0.57)	$ (0.01)
Income (loss) from discontinued operations	0.01	0.08	(4.05)
Basic earnings per share	0.48	(0.49)	(4.06)
Diluted earnings (loss) per share
Income (loss) from continuing operations	0.47	(0.57)	(0.01)
Income (loss) from discontinued operations	0.01	0.08	(4.05)
Diluted earnings per share	$ 0.48	$ (0.49)	$ (4.06)
Weighted average shares outstanding
Basic	44,339	44,132	43,768
Diluted	44,614	44,132	43,768