Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 387,342	$ 406,413	$ 778,055	$ 808,631
Energy and related sales, net	981	2,001	2,110	2,667
Total revenues	388,323	408,414	780,165	811,298
Costs of products sold	357,887	365,691	692,800	710,732
Gross profit	30,436	42,723	87,365	100,566
Selling, general and administrative expenses	31,999	37,191	67,085	69,049
(Gains) losses on dispositions of plant, equipment and timberlands, net	(58)	2	(26)	26
Operating income (loss)	(1,505)	5,530	20,306	31,491
Non-operating income (expense)
Interest expense	(4,476)	(3,953)	(8,484)	(8,069)
Interest income	45	61	158	152
Other, net	(149)	317	(428)	(383)
Total non-operating expense	(4,580)	(3,575)	(8,754)	(8,300)
(Loss) income before income taxes	(6,085)	1,955	11,552	23,191
Income tax provision (benefit)	(371)	(10)	5,663	5,058
Net income (loss)	$ (5,714)	$ 1,965	$ 5,889	$ 18,133
(Loss) earnings per share
Basic	$ (0.13)	$ 0.05	$ 0.14	$ 0.42
Diluted	(0.13)	0.04	0.13	0.41
Cash dividends declared per common share	$ 0.13	$ 0.125	$ 0.26	$ 0.25
Weighted average shares outstanding
Basic	43,604	43,558	43,593	43,539
Diluted	43,604	44,062	44,449	43,963