Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Condensed Income Statements, Captions [Line Items]
Net sales	$ 405,301	$ 419,960	$ 1,213,932	$ 1,248,232
Energy and related sales, net	1,346	1,153	4,013	3,936
Total revenues	406,647	421,113	1,217,945	1,252,168
Costs of products sold	345,477	361,205	1,056,209	1,107,319
Gross profit	61,170	59,908	161,736	144,849
Selling, general and administrative expenses	35,747	39,792	104,796	100,201
Losses (gains) on dispositions of plant, equipment and timberlands, net	5	(123)	31	(2,888)
Operating income	25,418	20,239	56,909	47,536
Other non-operating income (expense)
Interest expense	(3,895)	(4,317)	(11,964)	(13,177)
Interest income	52	90	204	232
Other, net	(573)	(220)	(956)	(192)
Total non-operating expense	(4,416)	(4,447)	(12,716)	(13,137)
Income before income taxes	21,002	15,792	44,193	34,399
Income tax provision (benefit)	1,401	2,288	6,459	4,122
Net income	19,601	13,504	37,734	30,277
Other comprehensive income (loss)	(69)	(3,002)	4,134	(21,200)
Comprehensive income	19,532	10,502	41,868	9,077
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	(16,760)	(19,437)	(52,634)	(59,655)
Total revenues	(16,760)	(19,437)	(52,634)	(59,655)
Costs of products sold	(16,760)	(19,437)	(52,634)	(59,655)
Other non-operating income (expense)
Interest expense	1,189	23,230	3,425	36,559
Interest income	(1,189)	(23,231)	(3,425)	(36,559)
Equity in earnings of subsidiaries	(33,453)	(4,808)	(90,535)	(60,654)
Total non-operating expense	(33,453)	(4,809)	(90,535)	(60,654)
Income before income taxes	(33,453)	(4,809)	(90,535)	(60,654)
Net income	(33,453)	(4,809)	(90,535)	(60,654)
Other comprehensive income (loss)	4,769	13,706	5,526	9,451
Comprehensive income	(28,684)	8,897	(85,009)	(51,203)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	211,761	222,803	638,918	655,599
Energy and related sales, net	1,346	1,153	4,013	3,936
Total revenues	213,107	223,956	642,931	659,535
Costs of products sold	186,297	197,906	582,751	614,060
Gross profit	26,810	26,050	60,180	45,475
Selling, general and administrative expenses	21,048	24,764	62,115	57,607
Losses (gains) on dispositions of plant, equipment and timberlands, net	7	(4)	11	(1,526)
Operating income	5,755	1,290	(1,946)	(10,606)
Other non-operating income (expense)
Interest expense	(4,332)	(4,346)	(13,036)	(13,771)
Interest income	173	181	523	513
Equity in earnings of subsidiaries	17,228	14,173	46,485	48,775
Other, net	(670)	(961)	(1,787)	(2,423)
Total non-operating expense	12,399	9,047	32,185	33,094
Income before income taxes	18,154	10,337	30,239	22,488
Income tax provision (benefit)	(1,447)	(3,167)	(7,495)	(7,789)
Net income	19,601	13,504	37,734	30,277
Other comprehensive income (loss)	(69)	(3,002)	4,134	(21,200)
Comprehensive income	19,532	10,502	41,868	9,077
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	18,086	19,005	54,293	61,822
Total revenues	18,086	19,005	54,293	61,822
Costs of products sold	16,732	17,299	51,493	58,554
Gross profit	1,354	1,706	2,800	3,268
Selling, general and administrative expenses	(25)	(8)	(246)	947
Losses (gains) on dispositions of plant, equipment and timberlands, net				(1,183)
Operating income	1,379	1,714	3,046	3,504
Other non-operating income (expense)
Interest expense	(1)		(1)
Interest income	1,063	23,129	3,056	36,226
Equity in earnings of subsidiaries	16,225	(9,366)	44,050	11,879
Other, net	(819)	23	(2,220)	(136)
Total non-operating expense	16,468	13,786	44,885	47,969
Income before income taxes	17,847	15,500	47,931	51,473
Income tax provision (benefit)	619	1,270	1,446	2,586
Net income	17,228	14,230	46,485	48,887
Other comprehensive income (loss)	(2,307)	(5,954)	(2,691)	(30,607)
Comprehensive income	14,921	8,276	43,794	18,280
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	192,214	197,589	573,355	590,466
Total revenues	192,214	197,589	573,355	590,466
Costs of products sold	159,208	165,437	474,599	494,360
Gross profit	33,006	32,152	98,756	96,106
Selling, general and administrative expenses	14,724	15,036	42,927	41,647
Losses (gains) on dispositions of plant, equipment and timberlands, net	(2)	(119)	20	(179)
Operating income	18,284	17,235	55,809	54,638
Other non-operating income (expense)
Interest expense	(751)	(23,201)	(2,352)	(35,965)
Interest income	5	11	50	52
Other, net	916	718	3,051	2,367
Total non-operating expense	170	(22,472)	749	(33,546)
Income before income taxes	18,454	(5,237)	56,558	21,092
Income tax provision (benefit)	2,229	4,185	12,508	9,325
Net income	16,225	(9,422)	44,050	11,767
Other comprehensive income (loss)	(2,462)	(7,752)	(2,835)	21,156
Comprehensive income	$ 13,763	$ (17,174)	$ 41,215	$ 32,923