Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net sales	$ 225,674	$ 231,560
Type of Revenue [Extensible List]	Product [Member]	Product [Member]
Costs of products sold	$ 186,378	$ 194,685
Type of Cost, Good or Service [Extensible List]	Product [Member]	Product [Member]
Gross profit	$ 39,296	$ 36,875
Selling, general and administrative expenses	22,827	24,594
Gains on dispositions of plant, equipment and timberlands, net	(850)
Operating income	17,319	12,281
Non-operating income (expense)
Interest expense	(1,531)	(1,778)
Interest income	20	264
Other, net	(224)	(753)
Total non-operating expense	(1,735)	(2,267)
Income from continuing operations before income taxes	15,584	10,014
Income tax provision	7,190	2,608
Net income	$ 8,394	$ 7,406
Basic earnings per share
Income from continuing operations	$ 0.19	$ 0.17
Basic earnings per share	0.19	0.17
Diluted earnings per share
Income from continuing operations	0.19	0.17
Diluted earnings per share	$ 0.19	$ 0.17
Weighted average shares outstanding
Basic	44,450	44,275
Diluted	44,869	44,530