Industry Segment and Foreign Operations - Long-lived Assets Including Goodwill and Total Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Property, plant, and equipment	$ 934,843	$ 942,703
Investment in unconsolidated joint venture	12,023	12,723
Goodwill	372,917	375,061
Total assets	2,654,608	2,460,957
Polymer
Segment Reporting Information [Line Items]
Property, plant, and equipment	521,304	523,067
Investment in unconsolidated joint venture	12,023	12,723
Goodwill	0	0
Total assets	1,259,912	1,104,954
Chemical
Segment Reporting Information [Line Items]
Property, plant, and equipment	413,539	419,636
Investment in unconsolidated joint venture	0	0
Goodwill	372,917	375,061
Total assets	$ 1,394,696	$ 1,356,003