Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net sales	$ 244,911	$ 216,183	$ 470,585	$ 447,743
Type of Revenue [Extensible List]	Product [Member]	Product [Member]	Product [Member]	Product [Member]
Costs of products sold	$ 209,357	$ 184,120	$ 395,735	$ 378,878
Type of Cost, Good or Service [Extensible List]	Product [Member]	Product [Member]	Product [Member]	Product [Member]
Gross profit	$ 35,554	$ 32,063	$ 74,850	$ 68,865
Selling, general and administrative expenses	28,984	23,551	51,811	48,072
Gains on dispositions of plant, equipment and timberlands, net	(1,553)	(597)	(2,403)	(597)
Operating income	8,123	9,109	25,442	21,390
Non-operating income (expense)
Interest expense	(1,772)	(1,759)	(3,303)	(3,537)
Interest income	11	87	31	351
Pension settlement expenses, net		(6,330)		(6,403)
Other, net	(849)	(835)	(1,073)	(1,515)
Total non-operating expense	(2,610)	(8,837)	(4,345)	(11,104)
Income from continuing operations before income taxes	5,513	272	21,097	10,286
Income tax provision	4,021	2,553	11,211	5,161
Income (loss) from continuing operations	1,492	(2,281)	9,886	5,125
Discontinued operations:
Loss before income taxes	(82)	(135)	(82)	(135)
Loss from discontinued operations	(82)	(135)	(82)	(135)
Net income (loss)	$ 1,410	$ (2,416)	$ 9,804	$ 4,990
Basic earnings per share
Income (loss) from continuing operations	$ 0.03	$ (0.05)	$ 0.22	$ 0.12
Loss from discontinued operations				(0.01)
Basic earnings per share	0.03	(0.05)	0.22	0.11
Diluted earnings per share
Income (loss) from continuing operations	0.03	(0.05)	0.22	0.12
Loss from discontinued operations				(0.01)
Diluted earnings per share	$ 0.03	$ (0.05)	$ 0.22	$ 0.11
Weighted average shares outstanding
Basic	44,563	44,343	44,507	44,309
Diluted	44,872	44,343	44,865	44,541