Net Sales - Summary of Net Sales Disaggregated by Principal Markets (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Net sales:
Net sales	$ 94,152	$ 100,450
Chemical [Member]
Net sales:
Net sales	94,152	100,450
Chemical [Member] \| Agricultural Products [Member]
Net sales:
Net sales	46,820	52,269
Chemical [Member] \| Industrial Acids and Other Chemical Products [Member]
Net sales:
Net sales	37,850	38,137
Chemical [Member] \| Mining Products [Member]
Net sales:
Net sales	$ 9,482	$ 10,044

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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