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Commitments - Summary of Contractual Obligations (Parenthetical) (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2017
MXN ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2016
MXN ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2015
MXN ($)
Dec. 31, 2017
MXN ($)
Disclosure of Detailed Information About Borrowings [Line Items]              
Future minimum lease payments $ 158           $ 3,105
Rental expense $ 115 $ 2,252 $ 121 $ 2,507 $ 114 $ 1,967  
Period for which lease payments made Next 10 years Next 10 years          
1-3 years [Member]              
Disclosure of Detailed Information About Borrowings [Line Items]              
Future minimum lease payments $ 79           1,552
3-5 Years [Member]              
Disclosure of Detailed Information About Borrowings [Line Items]              
Future minimum lease payments $ 48           $ 943