Segment Reporting - Reconciliation of Segment Information to Consolidated Financial Statements (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Operating income		$ 38,961	$ 42,916	$ 85,020	$ 87,523
Business restructuring		(586)	(1,061)	(1,372)	(1,061)
Interest expense, net		(2,863)	(3,417)	(5,855)	(7,031)
Other, net		965	(303)	2,228	(828)
Income Before Provision for Income Taxes		37,063	39,196	81,393	79,664
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income		57,726	60,014	118,637	121,789
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating income		31,030	27,232	69,267	64,477
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating income		21,257	30,994	42,656	53,191
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating income		5,439	1,788	6,714	4,121
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business restructuring		(586)	(1,061)	(1,372)	(1,061)
Unallocated corporate expenses	[1]	$ (18,179)	$ (16,037)	$ (32,245)	$ (33,205)

[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.