Segment Reporting - Reconciliation of Segment Information to Consolidated Financial Statements (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Operating income		$ 28,595	$ 36,914	$ 63,773	$ 59,437
Interest expense, net		(2,869)	(3,021)	(6,923)	(5,978)
Loss from equity in joint ventures		(1,815)	(1,243)	(3,055)	(2,694)
Other, net		235	556	887	530
Income Before Provision for Income Taxes		24,146	33,206	54,682	51,295
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating income		49,183	41,233	99,976	74,418
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating income		24,232	19,239	57,996	37,577
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating income		23,429	18,444	38,214	29,270
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating income		1,522	3,550	3,766	7,571
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated corporate expenses	[1]	$ (20,588)	$ (4,319)	$ (36,203)	$ (14,981)

[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.