Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Net sales	$ 405,301	$ 419,960	$ 1,213,932	$ 1,248,232
Energy and related sales, net	1,346	1,153	4,013	3,936
Total revenues	406,647	421,113	1,217,945	1,252,168
Costs of products sold	345,477	361,205	1,056,209	1,107,319
Gross profit	61,170	59,908	161,736	144,849
Selling, general and administrative expenses	35,747	39,792	104,796	100,201
Losses (gains) on dispositions of plant, equipment and timberlands, net	5	(123)	31	(2,888)
Operating income	25,418	20,239	56,909	47,536
Non-operating income (expense)
Interest expense	(3,895)	(4,317)	(11,964)	(13,177)
Interest income	52	90	204	232
Other, net	(573)	(220)	(956)	(192)
Total non-operating expense	(4,416)	(4,447)	(12,716)	(13,137)
Income before income taxes	21,002	15,792	44,193	34,399
Income tax provision	1,401	2,288	6,459	4,122
Net income	$ 19,601	$ 13,504	$ 37,734	$ 30,277
Earnings per share
Basic	$ 0.45	$ 0.31	$ 0.87	$ 0.70
Diluted	0.44	0.31	0.86	0.69
Cash dividends declared per common share	$ 0.125	$ 0.12	$ 0.375	$ 0.36
Weighted average shares outstanding
Basic	43,576	43,457	43,552	43,363
Diluted	44,133	43,865	44,059	43,949