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Defined Benefit Liabilities (Assets) - Principal Actuarial Assumptions (Detail)
Dec. 31, 2018
Dec. 31, 2017
Bottom of range [member]    
Disclosure of defined benefit plans [line items]    
Discount rate for defined benefit obligations 2.24% 2.58%
Expected rate of salary increase 3.42% 3.08%
Top of range [member]    
Disclosure of defined benefit plans [line items]    
Discount rate for defined benefit obligations 3.07% 4.03%
Expected rate of salary increase 5.61% 5.93%