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Employee Benefit - Sensitivity Analysis of One-percentage Point Change in Assumed Rates (Detail) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Discount rate [Member]    
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]    
Assumption - 1% increase $ (777) $ (721)
Assumption - 1% decrease 908 844
Rate of salary increase [Member]    
Disclosure of sensitivity analysis for actuarial assumptions [Line Items]    
Assumption - 1% increase 869 808
Assumption - 1% decrease $ (762) $ (707)