Industry Segments and Foreign Operations - Sales Revenue by Product Groups (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 510,947	$ 454,143	$ 1,494,392	$ 1,328,715
Cost of goods sold	382,228	318,887	1,075,051	967,744
Gross profit	128,719	135,256	419,341	360,971
Operating expenses:
Research and development	10,325	9,693	30,429	30,383
Selling, general, and administrative	42,579	42,769	124,436	135,845
Depreciation and amortization	34,307	31,977	102,040	93,913
Operating income	41,508	50,817	162,436	100,830
Disposition and exit of business activities	0	0	0	40,001
Loss on extinguishment of debt	(15,632)	0	(35,370)	(13,423)
Earnings of unconsolidated joint venture	125	94	370	274
Interest expense, net	(33,017)	(33,870)	(101,766)	(101,450)
Income (loss) before income taxes	(7,016)	17,041	25,670	26,232
Polymer
Segment Reporting Information [Line Items]
Revenue	314,159	272,970	920,225	786,132
Cost of goods sold	247,426	195,962	679,133	576,358
Gross profit	66,733	77,008	241,092	209,774
Operating expenses:
Research and development	7,347	6,920	21,690	22,008
Selling, general, and administrative	24,242	26,383	73,391	82,631
Depreciation and amortization	17,342	14,977	50,439	45,199
Operating income	17,802	28,728	95,572	59,936
Chemical
Segment Reporting Information [Line Items]
Revenue	196,788	181,173	574,167	542,583
Cost of goods sold	134,802	122,925	395,918	391,386
Gross profit	61,986	58,248	178,249	151,197
Operating expenses:
Research and development	2,978	2,773	8,739	8,375
Selling, general, and administrative	18,337	16,386	51,045	53,214
Depreciation and amortization	16,965	17,000	51,601	48,714
Operating income	$ 23,706	$ 22,089	66,864	$ 40,894
Aggregate amortization expense			$ 24,700