Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 231,560	$ 229,133
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Costs of products sold	$ 194,685	$ 193,516
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Gross profit	$ 36,875	$ 35,617
Selling, general and administrative expenses	24,594	24,622
Gains on dispositions of plant, equipment and timberlands, net		(669)
Operating income	12,281	11,664
Non-operating income (expense)
Interest expense	(1,778)	(4,746)
Interest income	264	505
Other, net	(753)	(962)
Total non-operating expense	(2,267)	(5,203)
Income from continuing operations before income taxes	10,014	6,461
Income tax provision	2,608	1,858
Income from continuing operations	7,406	4,603
Discontinued operations:
Income before income taxes		714
Income tax provision		31
Income from discontinued operations		683
Net income	$ 7,406	$ 5,286
Basic earnings per share
Income from continuing operations	$ 0.17	$ 0.10
Income from discontinued operations		0.02
Basic earnings per share	0.17	0.12
Diluted earnings per share
Income from continuing operations	0.17	0.10
Income from discontinued operations		0.02
Diluted earnings per share	0.17	0.12
Cash dividends declared per common share	$ 0.13	$ 0.13
Weighted average shares outstanding
Basic	44,275	44,027
Diluted	44,530	44,279