Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Income Statements, Captions [Line Items]
Net sales	$ 390,713	$ 402,218
Energy and related sales, net	1,129	666
Total revenues	391,842	402,884
Costs of products sold	334,913	345,041
Gross profit	56,929	57,843
Selling, general and administrative expenses	35,086	31,858
Losses on dispositions of plant, equipment and timberlands, net	32	24
Operating income	21,811	25,961
Other non-operating income (expense)
Interest expense	(4,008)	(4,116)
Interest income	113	91
Other, net	(279)	(700)
Total non-operating expense	(4,174)	(4,725)
Income before income taxes	17,637	21,236
Income tax provision	6,034	5,068
Net income	11,603	16,168
Other comprehensive income	7,193	15,742
Comprehensive income	18,796	31,910
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	205,771	217,888
Energy and related sales, net	1,129	666
Total revenues	206,900	218,554
Costs of products sold	183,946	191,959
Gross profit	22,954	26,595
Selling, general and administrative expenses	20,371	18,445
Losses on dispositions of plant, equipment and timberlands, net	32	2
Operating income	2,551	8,148
Other non-operating income (expense)
Interest expense	(4,661)	(4,415)
Interest income	149	181
Equity in earnings of subsidiaries	13,617	12,872
Other, net	493	(542)
Total non-operating expense	9,598	8,096
Income before income taxes	12,149	16,244
Income tax provision	546	76
Net income	11,603	16,168
Other comprehensive income	7,193	15,742
Comprehensive income	18,796	31,910
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	19,533	18,646
Total revenues	19,533	18,646
Costs of products sold	18,586	18,050
Gross profit	947	596
Selling, general and administrative expenses	74	(185)
Operating income	873	781
Other non-operating income (expense)
Interest expense	(113)
Interest income	1,161	992
Equity in earnings of subsidiaries	13,852	11,754
Other, net	(2,206)	20
Total non-operating expense	12,694	12,766
Income before income taxes	13,567	13,547
Income tax provision	(50)	675
Net income	13,617	12,872
Other comprehensive income	5,102	13,553
Comprehensive income	18,719	26,425
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	185,887	184,466
Total revenues	185,887	184,466
Costs of products sold	152,859	153,814
Gross profit	33,028	30,652
Selling, general and administrative expenses	14,641	13,598
Losses on dispositions of plant, equipment and timberlands, net		22
Operating income	18,387	17,032
Other non-operating income (expense)
Interest expense	(504)	(787)
Interest income	73	4
Other, net	1,434	(178)
Total non-operating expense	1,003	(961)
Income before income taxes	19,390	16,071
Income tax provision	5,538	4,317
Net income	13,852	11,754
Other comprehensive income	5,014	13,117
Comprehensive income	18,866	24,871
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	(20,478)	(18,782)
Total revenues	(20,478)	(18,782)
Costs of products sold	(20,478)	(18,782)
Other non-operating income (expense)
Interest expense	1,270	1,086
Interest income	(1,270)	(1,086)
Equity in earnings of subsidiaries	(27,469)	(24,626)
Total non-operating expense	(27,469)	(24,626)
Income before income taxes	(27,469)	(24,626)
Net income	(27,469)	(24,626)
Other comprehensive income	(10,116)	(26,670)
Comprehensive income	$ (37,585)	$ (51,296)