Segment Reporting - Reconciliation of Segment Information to Consolidated Financial Statements (Detail) - 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]
Operating income		$ 30,309	$ 28,738	$ 115,329	$ 116,261
Business restructuring		(426)		(1,798)	(1,061)
Interest expense, net		(2,763)	(2,824)	(8,618)	(9,855)
Other, net		1,766	1,229	3,994	401
Income Before Provision for Income Taxes		29,312	27,143	110,705	106,807
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income		44,570	50,152	163,207	171,941
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating income		22,466	20,737	91,733	85,214
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating income		21,116	27,087	63,772	80,278
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating income		988	2,328	7,702	6,449
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business restructuring		(426)		(1,798)	(1,061)
Unallocated corporate expenses	[1]	$ (13,835)	$ (21,414)	$ (46,080)	$ (54,619)

[1] Unallocated corporate expenses are primarily comprised of 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.