Segment Reporting - Operating Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Net Sales	$ 519,866	$ 495,101	$ 1,019,201	$ 963,370
Surfactants [Member]
Segment Reporting Information [Line Items]
Net Sales	356,884	329,334	715,824	651,937
Polymers [Member]
Segment Reporting Information [Line Items]
Net Sales	140,867	141,187	262,800	267,797
Specialty Products [Member]
Segment Reporting Information [Line Items]
Net Sales	$ 22,115	$ 24,580	$ 40,577	$ 43,636