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Other Current Liability - Summary of Revenue Recognized in Relation to Contract Liabilities (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year $ 744 $ 113
Advance from customers    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year 668  
Transportation Service    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year 17 28
Custodial service    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year $ 59 $ 85