Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 216,183	$ 235,053	$ 447,743	$ 464,186
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs of products sold	$ 184,120	$ 197,553	$ 378,878	$ 391,069
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 32,063	$ 37,500	$ 68,865	$ 73,117
Selling, general and administrative expenses	23,551	22,800	48,072	47,422
Gains on dispositions of plant, equipment and timberlands, net	(597)	(423)	(597)	(1,092)
Operating income	9,109	15,123	21,390	26,787
Non-operating income (expense)
Interest expense	(1,759)	(1,865)	(3,537)	(6,611)
Interest income	87	241	351	746
Pension settlement expenses, net	(6,330)		(6,403)
Other, net	(835)	(1,551)	(1,515)	(2,513)
Total non-operating expense	(8,837)	(3,175)	(11,104)	(8,378)
Income from continuing operations before income taxes	272	11,948	10,286	18,409
Income tax provision	2,553	5,655	5,161	7,513
Income (loss) from continuing operations	(2,281)	6,293	5,125	10,896
Discontinued operations:
Income (loss) before income taxes	(135)	(485)	(135)	229
Income tax provision (benefit)		(23)		8
Income (loss) from discontinued operations	(135)	(462)	(135)	221
Net income (loss)	$ (2,416)	$ 5,831	$ 4,990	$ 11,117
Basic earnings (loss) per share
Income (loss) from continuing operations	$ (0.05)	$ 0.14	$ 0.12	$ 0.25
Income (loss) from discontinued operations		(0.01)	(0.01)	0.01
Basic earnings (loss) per share	(0.05)	0.13	0.11	0.26
Diluted earnings (loss) per share
Income (loss) from continuing operations	(0.05)	0.14	0.12	0.25
Income (loss) from discontinued operations		(0.01)	(0.01)
Diluted earnings (loss) per share	(0.05)	0.13	0.11	0.25
Cash dividends declared per common share	$ 0.135	$ 0.13	$ 0.265	$ 0.26
Weighted average shares outstanding
Basic	44,343	44,140	44,309	44,084
Diluted	44,343	44,382	44,541	44,351