Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 Country Segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable operating segments \| Segment	3
Number of commercial clean coal production facilities	34
Number of countries in which the company has operations	33
Number of countries in which the company does business through a network of correspondent brokers and consultants	150
Description of contracts renewal period	One year or less
Percentage of commission and fee revenues on the effective date	70.00%
Percentage of commission and fee revenues in the first three months	20.00%
Percentage of commission and fee revenues after the first three months	10.00%

Description of contracts renewal period.

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Number of commercial clean coal production facilities.

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- Definition

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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- Definition

Percentage of Commissions and fee revenues recongized after the first three months of the underlying insurance contract.

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No definition available.

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- Definition

Percentage of Commissions and fee revenues recongized in the first three months of the underlying insurance contract.

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No definition available.

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- Definition

Percentage of Commissions and fee revenues recongized on the effective date of the underlying insurance contract.

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No definition available.

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- Definition

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.

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No definition available.

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