Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Income Statements, Captions [Line Items]
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 (loss)	20,239	44,217	47,536	77,120
Other 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 (loss) before income taxes	15,792	39,409	34,399	63,123
Income tax provision (benefit)	2,288	9,037	4,122	13,434
Net income (loss)	13,504	30,372	30,277	49,689
Other comprehensive income (loss)	(3,002)	(29,577)	(21,200)	(23,586)
Comprehensive income (loss)	10,502	795	9,077	26,103
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	(19,437)	(17,524)	(59,655)	(55,211)
Total revenues	(19,437)	(17,524)	(59,655)	(55,211)
Costs of products sold	(19,437)	(17,524)	(59,655)	(55,211)
Other non-operating income (expense)
Interest expense	23,230	90,217	36,559	95,682
Interest income	(23,231)	(90,218)	(36,559)	(95,683)
Equity in earnings of subsidiaries	(4,808)	59,566	(60,654)	(18,555)
Other, net		5		5
Total non-operating expense	(4,809)	59,570	(60,654)	(18,551)
Income (loss) before income taxes	(4,809)	59,570	(60,654)	(18,551)
Net income (loss)	(4,809)	59,570	(60,654)	(18,551)
Other comprehensive income (loss)	13,706	8,919	9,451	7,485
Comprehensive income (loss)	8,897	68,489	(51,203)	(11,066)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	222,803	236,182	655,599	679,877
Energy and related sales, net	1,153	860	3,936	6,912
Total revenues	223,956	237,042	659,535	686,789
Costs of products sold	197,906	197,182	614,060	629,984
Gross profit	26,050	39,860	45,475	56,805
Selling, general and administrative expenses	24,764	19,352	57,607	53,699
Gains on dispositions of plant, equipment and timberlands, net	(4)	(1,590)	(1,526)	(2,565)
Operating income (loss)	1,290	22,098	(10,606)	5,671
Other non-operating income (expense)
Interest expense	(4,346)	(4,790)	(13,771)	(14,284)
Interest income	181	152	513	468
Equity in earnings of subsidiaries	14,173	14,935	48,775	56,784
Other, net	(961)	(383)	(2,423)	(1,603)
Total non-operating expense	9,047	9,914	33,094	41,365
Income (loss) before income taxes	10,337	32,012	22,488	47,036
Income tax provision (benefit)	(3,167)	1,640	(7,789)	(2,653)
Net income (loss)	13,504	30,372	30,277	49,689
Other comprehensive income (loss)	(3,002)	(29,577)	(21,200)	(23,586)
Comprehensive income (loss)	10,502	795	9,077	26,103
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	19,005	17,735	61,822	56,138
Total revenues	19,005	17,735	61,822	56,138
Costs of products sold	17,299	17,019	58,554	53,491
Gross profit	1,706	716	3,268	2,647
Selling, general and administrative expenses	(8)	589	947	1,431
Gains on dispositions of plant, equipment and timberlands, net			(1,183)	(1,316)
Operating income (loss)	1,714	127	3,504	2,532
Other non-operating income (expense)
Interest income	23,129	89,951	36,226	95,165
Equity in earnings of subsidiaries	(9,366)	(74,502)	11,879	(38,229)
Other, net	23	9	(136)	30
Total non-operating expense	13,786	15,458	47,969	56,966
Income (loss) before income taxes	15,500	15,585	51,473	59,498
Income tax provision (benefit)	1,270	1,091	2,586	2,719
Net income (loss)	14,230	14,494	48,887	56,779
Other comprehensive income (loss)	(5,954)	(25,843)	(30,607)	(26,392)
Comprehensive income (loss)	8,276	(11,349)	18,280	30,387
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	197,589	228,699	590,466	685,350
Total revenues	197,589	228,699	590,466	685,350
Costs of products sold	165,437	188,762	494,360	567,812
Gross profit	32,152	39,937	96,106	117,538
Selling, general and administrative expenses	15,036	17,946	41,647	48,622
Gains on dispositions of plant, equipment and timberlands, net	(119)		(179)
Operating income (loss)	17,235	21,991	54,638	68,916
Other non-operating income (expense)
Interest expense	(23,201)	(90,098)	(35,965)	(95,643)
Interest income	11	145	52	193
Other, net	718	202	2,367	1,673
Total non-operating expense	(22,472)	(89,751)	(33,546)	(93,777)
Income (loss) before income taxes	(5,237)	(67,760)	21,092	(24,861)
Income tax provision (benefit)	4,185	6,306	9,325	13,368
Net income (loss)	(9,422)	(74,066)	11,767	(38,229)
Other comprehensive income (loss)	(7,752)	16,924	21,156	18,907
Comprehensive income (loss)	$ (17,174)	$ (57,142)	$ 32,923	$ (19,322)