Segment Reporting - Reconciliation of Segment Information to Income Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Operating Income		$ 40,213	$ 42,395	$ 150,784	$ 127,022
Business restructuring		(72)	(126)	(267)	(708)
Other Income (Expense)
Interest, net		(1,599)	(1,626)	(4,690)	(4,115)
Other, net		702	2,629	4,206	3,804
Income before provision for income taxes		39,316	43,398	150,300	126,711
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income		56,647	65,131	206,339	180,043
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating Income		34,452	41,151	133,558	125,810
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating Income		19,753	22,387	60,729	45,430
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating Income		2,442	1,593	12,052	8,803
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated corporate expenses	[1]	$ (16,362)	$ (22,610)	$ (55,288)	$ (52,313)

[1] Unallocated corporate expenses primarily comprise corporate administrative expenses (e.g., corporate finance, legal, human resources, information systems, deferred compensation and environmental remediation) that are not included in segment operating income and not used to evaluate segment performance.