Business Restructuring - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018 USD ($) Employees	Mar. 31, 2017 USD ($)
Restructuring Cost And Reserve [Line Items]
Business restructuring	$ 358,000	$ 786,000
Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring	358,000
Longford Mills [Member] | Surfactants [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring	$ 5,197,000
Number positions eliminated | Employees	30
Longford Mills [Member] | Surfactants [Member] | Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring	$ 1,594,000
Longford Mills [Member] | Surfactants [Member] | Other Expense [Member]
Restructuring Cost And Reserve [Line Items]
Business restructuring	$ 3,603,000