Segment Reporting - Operating Segment (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]
Net Sales	$ 487,814	$ 445,030	$ 1,451,184	$ 1,345,530
Surfactants [Member]
Segment Reporting Information [Line Items]
Net Sales	321,444	290,467	973,381	899,014
Polymers [Member]
Segment Reporting Information [Line Items]
Net Sales	147,754	134,144	415,551	382,540
Specialty Products [Member]
Segment Reporting Information [Line Items]
Net Sales	$ 18,616	$ 20,419	$ 62,252	$ 63,976