Net Sales - Summary of Net Sales Disaggregated by Principal Markets (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net sales:
Net sales	$ 73,896	$ 75,495	$ 121,527	$ 94,152	$ 94,730	$ 79,781	$ 103,199	$ 100,450	$ 365,070	$ 378,160	$ 427,504
Chemical [Member]
Net sales:
Net sales									365,070	378,160	427,504
Chemical [Member] | Agricultural Products [Member]
Net sales:
Net sales									187,641	187,164	184,054
Chemical [Member] | Industrial Acids and Other Chemical Products [Member]
Net sales:
Net sales									139,643	148,598	196,029
Chemical [Member] | Mining Products [Member]
Net sales:
Net sales									$ 37,786	$ 42,398	38,854
Chemical [Member] | Other Products [Member]
Net sales:
Net sales											$ 8,567