Condensed Consolidating Financial Statements - Condensed Consolidating Statements of Income and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Condensed Income Statements, Captions [Line Items]
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 (loss)	10,605	6,331	32,903	30,292
Other 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 other non-operating income (expense)	(4,649)	(4,293)	(9,189)	(7,785)
Income (loss) before income taxes	5,956	2,038	23,714	22,507
Income tax provision (benefit)	1,287	1,105	4,397	5,945
Net income	4,669	933	19,317	16,562
Other comprehensive income (loss)	3,026	7,105	5,991	(584)
Comprehensive income (loss)	7,695	8,038	25,308	15,978
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	(5)	(8)	(21)	(13)
Total revenues	(5)	(8)	(21)	(13)
Costs of products sold	(5)	(8)	(21)	(13)
Other non-operating income (expense)
Interest expense	2,809	1,861	5,465	3,549
Interest income	(2,809)	(1,861)	(5,465)	(3,550)
Other, net	(19,022)	(12,672)	(41,520)	(25,119)
Total other non-operating income (expense)	(19,022)	(12,672)	(41,520)	(25,120)
Income (loss) before income taxes	(19,022)	(12,672)	(41,520)	(25,120)
Net income	(19,022)	(12,672)	(41,520)	(25,120)
Other comprehensive income (loss)	(548)	(4,498)	(1,434)	8,088
Comprehensive income (loss)	(19,570)	(17,170)	(42,954)	(17,032)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	217,864	216,985	443,695	444,101
Energy and related sales, net	790	424	6,052	1,525
Total revenues	218,654	217,409	449,747	445,626
Costs of products sold	215,756	210,978	432,472	409,926
Gross profit	2,898	6,431	17,275	35,700
Selling, general and administrative expenses	16,555	16,928	34,347	38,054
Gains on dispositions of plant, equipment and timberlands, net	(162)	(17)	(974)	(90)
Operating income (loss)	(13,495)	(10,480)	(16,098)	(2,264)
Other non-operating income (expense)
Interest expense	(4,756)	(4,703)	(9,494)	(9,419)
Interest income	164	176	316	260
Other, net	18,683	12,139	40,300	24,095
Total other non-operating income (expense)	14,091	7,612	31,122	14,936
Income (loss) before income taxes	596	(2,868)	15,024	12,672
Income tax provision (benefit)	(4,073)	(3,801)	(4,293)	(3,890)
Net income	4,669	933	19,317	16,562
Other comprehensive income (loss)	3,026	7,105	5,991	(584)
Comprehensive income (loss)	7,695	8,038	25,308	15,978
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	4	8	21	13
Total revenues	4	8	21	13
Costs of products sold	4	8	21	13
Selling, general and administrative expenses	143	88	156	102
Gains on dispositions of plant, equipment and timberlands, net	(1,316)		(1,317)
Operating income (loss)	1,173	(88)	1,161	(102)
Other non-operating income (expense)
Interest income	2,656	1,727	5,214	3,416
Other, net	11	(6)	21	(8)
Total other non-operating income (expense)	2,667	1,721	5,235	3,408
Income (loss) before income taxes	3,840	1,633	6,396	3,306
Income tax provision (benefit)	715	634	1,628	1,308
Net income	3,125	999	4,768	1,998
Other comprehensive income (loss)	(550)	1,379	(549)	(3,229)
Comprehensive income (loss)	2,575	2,378	4,219	(1,231)
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	227,478	208,982	457,367	387,055
Total revenues	227,478	208,982	457,367	387,055
Costs of products sold	188,939	174,573	378,165	324,540
Gross profit	38,539	34,409	79,202	62,515
Selling, general and administrative expenses	15,616	17,512	31,362	29,859
Gains on dispositions of plant, equipment and timberlands, net	(4)	(2)		(2)
Operating income (loss)	22,927	16,899	47,840	32,658
Other non-operating income (expense)
Interest expense	(2,815)	(1,672)	(5,545)	(2,485)
Interest income	41	4	48	22
Other, net	389	714	1,471	1,454
Total other non-operating income (expense)	(2,385)	(954)	(4,026)	(1,009)
Income (loss) before income taxes	20,542	15,945	43,814	31,649
Income tax provision (benefit)	4,645	4,272	7,062	8,527
Net income	15,897	11,673	36,752	23,122
Other comprehensive income (loss)	1,098	3,119	1,983	(4,859)
Comprehensive income (loss)	$ 16,995	$ 14,792	$ 38,735	$ 18,263