Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net sales	$ 390,713	$ 402,218
Energy and related sales, net	1,129	666
Total revenues	391,842	402,884
Costs of products sold	334,913	345,041
Gross profit	56,929	57,843
Selling, general and administrative expenses	35,086	31,858
Losses on dispositions of plant, equipment and timberlands, net	32	24
Operating income	21,811	25,961
Non-operating income (expense)
Interest expense	(4,008)	(4,116)
Interest income	113	91
Other, net	(279)	(700)
Total non-operating expense	(4,174)	(4,725)
Income before income taxes	17,637	21,236
Income tax provision	6,034	5,068
Net income	$ 11,603	$ 16,168
Earnings per share
Basic	$ 0.27	$ 0.37
Diluted	0.26	0.37
Cash dividends declared per common share	$ 0.13	$ 0.125
Weighted average shares outstanding
Basic	43,583	43,521
Diluted	44,493	43,871