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Other Current Monetary Assets - Annual Yield Rates of Time Deposits and Negotiable Certificates of Deposits with Maturities of more Than Three Months (Detail)
Dec. 31, 2017
Dec. 31, 2016
Bottom of range [Member]    
Disclosure of annual yield rates of other current monetary assets [Line Items]    
Time deposits and negotiable certificates of deposit with maturities of more than three months 0.06% 0.11%
Top of range [Member]    
Disclosure of annual yield rates of other current monetary assets [Line Items]    
Time deposits and negotiable certificates of deposit with maturities of more than three months 4.15% 1.95%