Net Sales - Summary of Net Sales Disaggregated by Principal Markets (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net sales:
Net sales	$ 75,495	$ 79,781	$ 291,174	$ 283,430
Chemical [Member]
Net sales:
Net sales	75,495	79,781	291,174	283,430
Chemical [Member] \| Agricultural Products [Member]
Net sales:
Net sales	35,494	35,998	154,790	146,291
Chemical [Member] \| Industrial Acids and Other Chemical Products [Member]
Net sales:
Net sales	30,552	34,788	105,579	105,700
Chemical [Member] \| Mining Products [Member]
Net sales:
Net sales	$ 9,449	$ 8,995	$ 30,805	$ 31,439

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration