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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net sales:
Net sales	$ 103,199	$ 122,853	$ 203,649	$ 246,197
Chemical [Member]
Net sales:
Net sales	103,199	122,853	203,649	246,197
Chemical [Member] \| Agricultural Products [Member]
Net sales:
Net sales	58,024	57,236	110,293	120,499
Chemical [Member] \| Industrial Acids and Other Chemical Products [Member]
Net sales:
Net sales	32,775	53,217	70,912	102,097
Chemical [Member] \| Mining Products [Member]
Net sales:
Net sales	$ 12,400	10,344	$ 22,444	17,960
Chemical [Member] \| Other Products [Member]
Net sales:
Net sales		$ 2,056		$ 5,641