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Financial Assets and Financial Liabilities - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Financial Instruments [Line Items]      
Dividends received $ 108,000 $ 109,000 $ 105,000
Maximum borrowing capacity 264,162,000 287,017,000  
Unused portion of the credit lines 200,000,000    
Interest-bearing loans and borrowings, current portion $ 10,131,000 $ 11,356,000  
Liquidity discount 30.00% 30.00%  
Line Of Credit 1 [Member]      
Disclosure Of Financial Instruments [Line Items]      
Unused portion of the credit lines $ 200,340,000 $ 207,928,000  
Letters of Credit [Member]      
Disclosure Of Financial Instruments [Line Items]      
Unused portion of the credit lines 95,034,000 113,255,000  
Open letters of credit [Member]      
Disclosure Of Financial Instruments [Line Items]      
Unused portion of the credit lines 18,077,000 15,209,000  
Foreign currency forward contracts [Member]      
Disclosure Of Financial Instruments [Line Items]      
Outstanding forward contracts, notional amount $ 0 $ (900,000)