Segment Reporting - Reconciliation of Segment Information to Consolidated Financial Statements (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Operating Income	[1],[2]	$ 29,738	$ 41,283
Business restructuring expenses (Note 17)		(733)	(358)
Interest expense, net		(1,853)	(3,151)
Other, net		3,145	1,160
Income Before Provision for Income Taxes	[1],[2]	31,030	39,292
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	52,403	58,423
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	37,167	41,468
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	12,105	17,305
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating Income		3,131	(350)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated corporate expenses	[3]	$ (21,932)	$ (16,782)

[1] The 2018 amounts for the noted line items have been changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.

[2] The 2018 amounts for the noted line items have been changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from the last in, first out (LIFO) basis to the first in, first out (FIFO) basis.

[3] 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.