Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Net sales	$ 399,917	$ 413,325	$ 387,342	$ 390,713	$ 390,865	$ 405,301	$ 406,413	$ 402,218	$ 1,591,297	$ 1,604,797	$ 1,661,084
Energy and related sales, net									5,126	6,141	5,664
Total revenues									1,596,423	1,610,938	1,666,748
Costs of products sold									1,403,913	1,392,335	1,463,783
Gross profit	$ 50,410	$ 54,735	$ 30,436	$ 56,929	$ 56,867	$ 61,170	$ 42,723	$ 57,843	192,510	218,603	202,965
Selling, general and administrative expenses									134,394	190,694	127,706
(Gains) losses on dispositions of plant, equipment and timberlands, net									26	216	(21,113)
Operating income									58,090	27,693	96,372
Other non-operating income (expense)
Interest expense									(17,772)	(15,822)	(17,464)
Interest income									237	206	283
Other, net									(1,220)	(1,271)	(615)
Total non-operating expense									(18,755)	(16,887)	(17,796)
Income before income taxes									39,335	10,806	78,576
Income tax provision (benefit)									31,421	(10,748)	14,001
Net income									7,914	21,554	64,575
Other comprehensive income (loss)									63,931	(14,120)	(35,616)
Comprehensive income									71,845	7,434	28,959
Adjustments/ Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales									(88,026)	(69,645)	(78,026)
Total revenues									(88,026)	(69,645)	(78,026)
Costs of products sold									(88,026)	(69,645)	(78,026)
Other non-operating income (expense)
Interest expense									5,394	4,715	37,542
Interest income									(5,394)	(4,715)	(37,543)
Equity in earnings of subsidiaries									(79,735)	(119,354)	(86,683)
Total non-operating expense									(79,735)	(119,354)	(86,684)
Income before income taxes									(79,735)	(119,354)	(86,684)
Net income									(79,735)	(119,354)	(86,684)
Other comprehensive income (loss)									(104,118)	51,092	11,330
Comprehensive income									(183,853)	(68,262)	(75,354)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales									790,933	843,582	875,026
Energy and related sales, net									5,126	6,141	5,664
Total revenues									796,059	849,723	880,690
Costs of products sold									747,736	763,109	811,329
Gross profit									48,323	86,614	69,361
Selling, general and administrative expenses									69,483	133,387	71,751
(Gains) losses on dispositions of plant, equipment and timberlands, net									223	177	(19,720)
Operating income									(21,383)	(46,950)	17,330
Other non-operating income (expense)
Interest expense									(20,394)	(17,436)	(18,147)
Interest income									599	687	673
Equity in earnings of subsidiaries									18,864	61,007	61,946
Other, net									2,241	(2,312)	(3,389)
Total non-operating expense									1,310	41,946	41,083
Income before income taxes									(20,073)	(5,004)	58,413
Income tax provision (benefit)									(27,987)	(26,558)	(6,162)
Net income									7,914	21,554	64,575
Other comprehensive income (loss)									63,931	(14,120)	(35,616)
Comprehensive income									71,845	7,434	28,959
Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales									89,787	75,000	84,704
Total revenues									89,787	75,000	84,704
Costs of products sold									85,196	70,991	80,455
Gross profit									4,591	4,009	4,249
Selling, general and administrative expenses									2,598	156	821
(Gains) losses on dispositions of plant, equipment and timberlands, net									(188)		(1,183)
Operating income									2,181	4,165	4,611
Other non-operating income (expense)
Interest expense									(971)	(41)
Interest income									4,947	4,177	37,127
Equity in earnings of subsidiaries									60,871	58,347	24,737
Other, net									(6,776)	(3,966)	(1,471)
Total non-operating expense									58,071	58,517	60,393
Income before income taxes									60,252	62,682	65,004
Income tax provision (benefit)									41,388	1,675	2,922
Net income									18,864	61,007	62,082
Other comprehensive income (loss)									52,290	(25,916)	(41,010)
Comprehensive income									71,154	35,091	21,072
Non Guarantors [Member]
Condensed Income Statements, Captions [Line Items]
Net sales									798,603	755,860	779,380
Total revenues									798,603	755,860	779,380
Costs of products sold									659,007	627,880	650,025
Gross profit									139,596	127,980	129,355
Selling, general and administrative expenses									62,313	57,463	55,134
(Gains) losses on dispositions of plant, equipment and timberlands, net									(9)	39	(210)
Operating income									77,292	70,478	74,431
Other non-operating income (expense)
Interest expense									(1,801)	(3,060)	(36,859)
Interest income									85	57	26
Other, net									3,315	5,007	4,245
Total non-operating expense									1,599	2,004	(32,588)
Income before income taxes									78,891	72,482	41,843
Income tax provision (benefit)									18,020	14,135	17,241
Net income									60,871	58,347	24,602
Other comprehensive income (loss)									51,828	(25,176)	29,680
Comprehensive income									$ 112,699	$ 33,171	$ 54,282