Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Net sales	$ 445,341	$ 425,967	$ 901,062	$ 831,156
Energy and related sales, net	790	424	6,052	1,525
Total revenues	446,131	426,391	907,114	832,681
Costs of products sold	404,694	385,551	810,637	734,466
Gross profit	41,437	40,840	96,477	98,215
Selling, general and administrative expenses	32,314	34,528	65,865	68,015
Gains on dispositions of plant, equipment and timberlands, net	(1,482)	(19)	(2,291)	(92)
Operating income	10,605	6,331	32,903	30,292
Non-operating income (expense)
Interest expense	(4,762)	(4,514)	(9,574)	(8,355)
Interest income	52	46	113	148
Other, net	61	175	272	422
Total non-operating expense	(4,649)	(4,293)	(9,189)	(7,785)
Income before income taxes	5,956	2,038	23,714	22,507
Income tax provision	1,287	1,105	4,397	5,945
Net income	$ 4,669	$ 933	$ 19,317	$ 16,562
Earnings per share
Basic	$ 0.11	$ 0.02	$ 0.45	$ 0.38
Diluted	$ 0.11	$ 0.02	$ 0.44	$ 0.38
Cash dividends declared per common share	$ 0.11	$ 0.10	$ 0.22	$ 0.20
Weighted average shares outstanding
Basic	43,287	43,134	43,327	43,050
Diluted	44,136	44,202	44,251	44,119