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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Operating Income	[1],[2]	$ 27,966	$ 27,145	$ 98,769	$ 113,814
Business restructuring expenses (Note 17)		(459)	(1,715)	(1,642)	(2,346)
Interest expense, net		(1,402)	(2,797)	(5,021)	(8,620)
Other, net		885	346	4,265	1,990
Income Before Provision for Income Taxes	[1],[2]	27,449	24,694	98,013	107,184
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	45,204	50,736	158,435	167,776
Operating Segments [Member] | Surfactants [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	19,660	28,824	88,913	104,370
Operating Segments [Member] | Polymers [Member]
Segment Reporting Information [Line Items]
Operating Income	[1]	23,283	19,259	58,148	56,863
Operating Segments [Member] | Specialty Products [Member]
Segment Reporting Information [Line Items]
Operating Income		2,261	2,653	11,374	6,543
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Unallocated corporate expenses	[3]	$ (16,779)	$ (21,876)	$ (58,024)	$ (51,616)

[1] The 2018 amounts for the noted line items have been retrospectively 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 retrospectively 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.