Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended							9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales	$ 390,865	$ 405,301	$ 406,413	$ 402,218	$ 412,852	$ 410,803	$ 417,469	$ 419,960	$ 1,604,797	$ 1,661,084	$ 1,802,415
Energy and related sales, net									6,141	5,664	7,927
Total revenues									1,610,938	1,666,748	1,810,342
Costs of products sold									1,392,335	1,463,783	1,575,188
Gross profit	$ 56,867	$ 61,170	$ 42,723	$ 57,843	$ 58,116	$ 32,833	$ 52,108	$ 59,908	218,603	202,965	235,154
Selling, general and administrative expenses									190,694	127,706	133,235
Losses (gains) on dispositions of plant, equipment and timberlands, net									216	(21,113)	(4,861)
Operating income									27,693	96,372	106,780
Non-operating income (expense)
Interest expense									15,822	17,464	18,921
Interest income									206	283	159
Other, net									(1,271)	(615)	(635)
Total non-operating expense									(16,887)	(17,796)	(19,397)
Income before income taxes									10,806	78,576	87,383
Income tax provision (benefit)									(10,748)	14,001	18,137
Net income									$ 21,554	$ 64,575	$ 69,246
Earnings per share
Basic									$ 0.49	$ 1.49	$ 1.60
Diluted									0.49	1.47	1.57
Cash dividends declared per common share									$ 0.50	$ 0.48	$ 0.44
Weighted average shares outstanding
Basic									43,558	43,397	43,201
Diluted									44,129	43,942	44,066