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Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021 Country Segment Facility
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of reportable segments | Segment	3
Number of commercial clean coal production facilities | Facility	35
Number of countries in which the company has operations	56
Number of countries in which the company does business through a network of correspondent brokers and consultants	150

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Number of commercial clean coal production facilities.

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Number of Countries in which the Company does Business through a Network of Correspondent Brokers and Consultants

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Number of Countries in which the Company has Operations

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

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