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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Adoption of ASC 606 - Summary of Net Sales Disaggregated by Revenue Source (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net sales:
Net sales	$ 79,781	$ 92,390	$ 283,430	$ 338,587
Chemical [Member]
Net sales:
Net sales	79,781	92,390	283,430	338,587
Chemical [Member] \| Agricultural Products [Member]
Net sales:
Net sales	35,998	31,154	146,291	151,653
Chemical [Member] \| Industrial Acids and Other Chemical Products [Member]
Net sales:
Net sales	34,788	47,450	105,700	149,546
Chemical [Member] \| Mining Products [Member]
Net sales:
Net sales	$ 8,995	10,861	$ 31,439	28,821
Chemical [Member] \| Other Products [Member]
Net sales:
Net sales		$ 2,925		$ 8,567