Customer Claims - Additional Information (Detail) - Surfactants [Member]	3 Months Ended			12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2017 USD ($) Claim	Dec. 31, 2016 Claim	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Number of customer claims | Claim			2
Insurance claims reserve amount | $				$ 7,367,000
Claim paid | $	$ 703,000	$ 2,709,000
Number of claims and reversed | Claim		1