Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net sales	$ 233,473	$ 232,515	$ 681,216	$ 696,701
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Costs of products sold	$ 195,222	$ 194,494	$ 574,100	$ 585,563
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 38,251	$ 38,021	$ 107,116	$ 111,138
Selling, general and administrative expenses	24,635	23,721	72,707	71,143
Gains on dispositions of plant, equipment and timberlands, net	(413)	(235)	(1,010)	(1,327)
Operating income	14,029	14,535	35,419	41,322
Non-operating income (expense)
Interest expense	(1,810)	(1,902)	(5,347)	(8,513)
Interest income	39	185	390	931
Pension settlement expenses, net	(389)		(6,792)
Other, net	(1,728)	(1,034)	(3,243)	(3,547)
Total non-operating expense	(3,888)	(2,751)	(14,992)	(11,129)
Income from continuing operations before income taxes	10,141	11,784	20,427	30,193
Income tax provision	3,614	3,141	8,775	10,654
Income from continuing operations	6,527	8,643	11,652	19,539
Discontinued operations:
Income (loss) before income taxes		1,062	(135)	1,291
Income tax provision (benefit)		(2,519)		(2,511)
Income (loss) from discontinued operations	0	3,581	(135)	3,802
Net income	$ 6,527	$ 12,224	$ 11,517	$ 23,341
Basic earnings per share
Income from continuing operations	$ 0.15	$ 0.19	$ 0.26	$ 0.44
Income from discontinued operations		0.09		0.09
Basic earnings per share	0.15	0.28	0.26	0.53
Diluted earnings per share
Income from continuing operations	0.15	0.19	0.26	0.44
Income from discontinued operations		0.09		0.09
Diluted earnings per share	0.15	0.28	0.26	0.53
Cash dividends declared per common share	$ 0.135	$ 0.13	$ 0.40	$ 0.39
Weighted average shares outstanding
Basic	44,368	44,171	44,329	44,113
Diluted	44,636	44,442	44,549	44,405