Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Income Statements, Captions [Line Items]
Net sales	$ 387,342	$ 406,413	$ 778,055	$ 808,631
Energy and related sales, net	981	2,001	2,110	2,667
Total revenues	388,323	408,414	780,165	811,298
Costs of products sold	357,887	365,691	692,800	710,732
Gross profit	30,436	42,723	87,365	100,566
Selling, general and administrative expenses	31,999	37,191	67,085	69,049
(Gains) losses on dispositions of plant, equipment and timberlands, net	(58)	2	(26)	26
Operating income (loss)	(1,505)	5,530	20,306	31,491
Other non-operating income (expense)
Interest expense	(4,476)	(3,953)	(8,484)	(8,069)
Interest income	45	61	158	152
Other, net	(149)	317	(428)	(383)
Total non-operating expense	(4,580)	(3,575)	(8,754)	(8,300)
(Loss) income before income taxes	(6,085)	1,955	11,552	23,191
Income tax provision (benefit)	(371)	(10)	5,663	5,058
Net income (loss)	(5,714)	1,965	5,889	18,133
Other comprehensive income	26,332	(11,539)	33,525	4,203
Comprehensive income (loss)	20,618	(9,574)	39,414	22,336
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	191,370	209,269	397,141	427,157
Energy and related sales, net	981	2,001	2,110	2,667
Total revenues	192,351	211,270	399,251	429,824
Costs of products sold	195,444	204,495	379,390	396,454
Gross profit	(3,093)	6,775	19,861	33,370
Selling, general and administrative expenses	16,875	22,622	37,246	41,067
(Gains) losses on dispositions of plant, equipment and timberlands, net	16	2	48	4
Operating income (loss)	(19,984)	(15,849)	(17,433)	(7,701)
Other non-operating income (expense)
Interest expense	(5,182)	(4,289)	(9,843)	(8,704)
Interest income	142	169	291	350
Equity in earnings of subsidiaries	18,801	16,385	32,418	29,257
Other, net	534	(575)	1,027	(1,117)
Total non-operating expense	14,295	11,690	23,893	19,786
(Loss) income before income taxes	(5,689)	(4,159)	6,460	12,085
Income tax provision (benefit)	25	(6,124)	571	(6,048)
Net income (loss)	(5,714)	1,965	5,889	18,133
Other comprehensive income	26,332	(11,539)	33,525	4,203
Comprehensive income (loss)	20,618	(9,574)	39,414	22,336
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	23,052	17,561	42,585	36,207
Total revenues	23,052	17,561	42,585	36,207
Costs of products sold	22,047	16,711	40,633	34,761
Gross profit	1,005	850	1,952	1,446
Selling, general and administrative expenses	236	(36)	310	(221)
(Gains) losses on dispositions of plant, equipment and timberlands, net	(74)		(74)
Operating income (loss)	843	886	1,716	1,667
Other non-operating income (expense)
Interest expense	(206)		(319)
Interest income	1,237	1,001	2,398	1,993
Equity in earnings of subsidiaries	19,249	16,071	33,101	27,825
Other, net	(2,319)	(1,421)	(4,525)	(1,401)
Total non-operating expense	17,961	15,651	30,655	28,417
(Loss) income before income taxes	18,804	16,537	32,371	30,084
Income tax provision (benefit)	3	152	(47)	827
Net income (loss)	18,801	16,385	32,418	29,257
Other comprehensive income	23,964	(13,937)	29,066	(384)
Comprehensive income (loss)	42,765	2,448	61,484	28,873
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	194,708	196,675	380,595	381,141
Total revenues	194,708	196,675	380,595	381,141
Costs of products sold	162,184	161,577	315,043	315,391
Gross profit	32,524	35,098	65,552	65,750
Selling, general and administrative expenses	14,888	14,605	29,529	28,203
(Gains) losses on dispositions of plant, equipment and timberlands, net				22
Operating income (loss)	17,636	20,493	36,023	37,525
Other non-operating income (expense)
Interest expense	(437)	(814)	(941)	(1,601)
Interest income	15	41	88	45
Other, net	1,636	2,313	3,070	2,135
Total non-operating expense	1,214	1,540	2,217	579
(Loss) income before income taxes	18,850	22,033	38,240	38,104
Income tax provision (benefit)	(399)	5,962	5,139	10,279
Net income (loss)	19,249	16,071	33,101	27,825
Other comprehensive income	23,371	(13,490)	28,385	(373)
Comprehensive income (loss)	42,620	2,581	61,486	27,452
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	(21,788)	(17,092)	(42,266)	(35,874)
Total revenues	(21,788)	(17,092)	(42,266)	(35,874)
Costs of products sold	(21,788)	(17,092)	(42,266)	(35,874)
Other non-operating income (expense)
Interest expense	1,349	1,150	2,619	2,236
Interest income	(1,349)	(1,150)	(2,619)	(2,236)
Equity in earnings of subsidiaries	(38,050)	(32,456)	(65,519)	(57,082)
Total non-operating expense	(38,050)	(32,456)	(65,519)	(57,082)
(Loss) income before income taxes	(38,050)	(32,456)	(65,519)	(57,082)
Net income (loss)	(38,050)	(32,456)	(65,519)	(57,082)
Other comprehensive income	(47,335)	27,427	(57,451)	757
Comprehensive income (loss)	$ (85,385)	$ (5,029)	$ (122,970)	$ (56,325)