Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Net sales	$ 419,960	$ 465,092	$ 1,248,232	$ 1,366,154
Energy and related sales, net	1,153	860	3,936	6,912
Total revenues	421,113	465,952	1,252,168	1,373,066
Costs of products sold	361,205	385,439	1,107,319	1,196,076
Gross profit	59,908	80,513	144,849	176,990
Selling, general and administrative expenses	39,792	37,886	100,201	103,751
Gains on dispositions of plant, equipment and timberlands, net	(123)	(1,590)	(2,888)	(3,881)
Operating income	20,239	44,217	47,536	77,120
Non-operating income (expense)
Interest expense	(4,317)	(4,671)	(13,177)	(14,245)
Interest income	90	30	232	143
Other, net	(220)	(167)	(192)	105
Total non-operating expense	(4,447)	(4,808)	(13,137)	(13,997)
Income before income taxes	15,792	39,409	34,399	63,123
Income tax provision	2,288	9,037	4,122	13,434
Net income	$ 13,504	$ 30,372	$ 30,277	$ 49,689
Earnings per share
Basic	$ 0.31	$ 0.71	$ 0.70	$ 1.15
Diluted	0.31	0.69	0.69	1.13
Cash dividends declared per common share	$ 0.12	$ 0.11	$ 0.36	$ 0.33
Weighted average shares outstanding
Basic	43,457	43,049	43,363	43,233
Diluted	43,865	43,841	43,949	44,111