Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements of Income [Abstract]
Net sales	$ 404,354	$ 416,493	$ 1,186,399	$ 1,211,249
Energy and related sales, net	1,867	2,840	5,358	7,887
Total revenues	406,221	419,333	1,191,757	1,219,136
Costs of products sold	347,029	364,417	1,030,717	1,066,553
Gross profit	59,192	54,916	161,040	152,583
Selling, general and administrative expenses	29,380	31,430	89,460	94,520
Gains on dispositions of plant, equipment and timberlands, net	(1,473)	(698)	(8,471)	(3,902)
Operating income	31,285	24,184	80,051	61,965
Non-operating income (expense)
Interest expense	(4,152)	(6,456)	(12,580)	(19,377)
Interest income	106	134	332	491
Other, net	(4)	(137)	295	(405)
Total other income (expense)	(4,050)	(6,459)	(11,953)	(19,291)
Income before income taxes	27,235	17,725	68,098	42,674
Income tax provision	7,136	4,699	15,689	9,721
Net income	$ 20,099	$ 13,026	$ 52,409	$ 32,953
Earnings per share
Basic	$ 0.47	$ 0.29	$ 1.22	$ 0.72
Diluted	$ 0.46	$ 0.28	$ 1.20	$ 0.71
Cash dividends declared per common share	$ 0.09	$ 0.09	$ 0.27	$ 0.27
Weighted average shares outstanding
Basic	42,837	45,299	42,814	45,813
Diluted	43,667	45,839	43,595	46,341