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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, 2020
Dec. 31, 2019
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year $ 209 $ 744
Advance from customers    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year 93 668
Transportation Service    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year 56 17
Custodial service    
Current contract liabilities    
Revenue recognized that was included in the contract liabilities balance at the beginning of the year $ 60 $ 59