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Balances and Transactions in Foreign Currencies - Summary of Exchange Rates (Detail)
Apr. 20, 2018
$ / EUR
$ / $
Dec. 31, 2017
$ / EUR
$ / $
Dec. 31, 2016
$ / EUR
$ / $
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate   19.6395  
U.S. dollars [member]      
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate   19.7354 20.6640
Euro [member]      
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate | $ / EUR   23.5729 21.7741
Changes in foreign exchange rates [member]      
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate 18.6145    
Changes in foreign exchange rates [member] | U.S. dollars [member]      
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate 18.0333    
Changes in foreign exchange rates [member] | Euro [member]      
Disclosure of exchange rates [Line Items]      
Closing foreign exchange rate | $ / EUR 22.9066