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Other Current Liability - Summary of Contract Liability (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Current contract liabilities    
Total current contract liabilities $ 259 $ 216
Advance from customers    
Current contract liabilities    
Total current contract liabilities 156 93
Custodial service    
Current contract liabilities    
Total current contract liabilities 44 63
Transportation Service    
Current contract liabilities    
Total current contract liabilities $ 59 $ 60