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Financial Risk Management Objectives - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Aug. 13, 2014
Disclosure Of Financial Instruments [Line Items]          
Copper costs as a percentage of product cost 85.00% 80.00%      
Cash and cash equivalents $ 60,778,000 $ 46,093,000 $ 48,231,000 $ 51,303,000  
Unutilized amounts of bank loans 182,000,000        
Financial liabilities 49,170,000 77,560,000     $ 0
Mortgage of land, buildings, machinery and equipment, investment properties and land use rights 9,084,000 8,633,000      
Pledge of other receivables 7,525,000 7,528,000      
Assets and uncalled capital pledged as security 1,200,000 1,181,000      
Subsidiary [Member]          
Disclosure Of Financial Instruments [Line Items]          
Assets and uncalled capital pledged as security $ 27,731,000 $ 32,715,000      
One major customer [Member]          
Disclosure Of Financial Instruments [Line Items]          
Percentage of trade receivables from one customer 8.20% 22.40%      
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 $ 64,000 $ 113,000      
Top of range [Member]          
Disclosure Of Financial Instruments [Line Items]          
Percentage of financial liabilities bear floating interest rate 40.00%        
Weighted average [Member]          
Disclosure Of Financial Instruments [Line Items]          
Weighted average interest rates on bank loans and overdrafts 3.68% 2.85%