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Property, Plant and Equipment - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of detailed information about property, plant and equipment [Line Items]      
Impairment loss $ 546,000 $ 11,000 $ 223,000
Vehicles [Member]      
Disclosure of detailed information about property, plant and equipment [Line Items]      
Carrying value of motor vehicles under financial leases 0 $ 66,000 $ 50,000
Siam Fiber Optics Co., Ltd. [Member]      
Disclosure of detailed information about property, plant and equipment [Line Items]      
Recoverable amount of CGU $ 0    
Key assumptions used in calculating the value in use, discount rate 14.80%