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Financial Risk Management Objectives - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Financial Instruments [Line Items]        
Copper costs as a percentage of product cost 82.00% 85.00%    
Cash and cash equivalents $ 53,673 $ 60,778 $ 46,093 $ 48,231
Unutilized amounts of bank loans 208,000      
Financial liabilities 35,000      
Mortgage of land, buildings, machinery and equipment, investment properties and land use rights 15,099 9,084    
Pledge of other receivables 4,847 7,525    
Assets and uncalled capital pledged as security 1,339 1,200    
Subsidiary [Member]        
Disclosure Of Financial Instruments [Line Items]        
Assets and uncalled capital pledged as security $ 27,454 $ 27,731    
One major customer [Member]        
Disclosure Of Financial Instruments [Line Items]        
Percentage of trade receivables from one customer 9.31% 8.20%    
Interest rate risk [Member]        
Disclosure Of Financial Instruments [Line Items]        
Change of interest rates 0.30% 0.30%    
Change in profit before tax due to change of interest rates $ 46 $ 64    
Top Of Range [Member]        
Disclosure Of Financial Instruments [Line Items]        
Percentage of financial liabilities bear floating interest rate 25.00%      
Weighted average [Member]        
Disclosure Of Financial Instruments [Line Items]        
Weighted average interest rates on bank loans and overdrafts 3.72% 3.68%