Accounts payable and Accrued Liabilities - Additional Information (Detail) - Vendor	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Accounts Payable And Accrued Expenses [Line Items]
Number of vendors	3	3
Accounts Payable [Member] \| Supplier Concentration Risk [Member]
Accounts Payable And Accrued Expenses [Line Items]
Percentage of amount due to major vendors accounts payable	37.00%	39.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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