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Financial Instruments - Summary of Net Effect of Expired contracts that did not Meet Hedging Criteria for Accounting Purposes (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2017
MXN ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
MXN ($)
Dec. 31, 2015
MXN ($)
Disclosure of net effect of changes in fair value of derivative financial instruments that did not meet hedging criteria for accounting purposes [Line Items]        
Market value (loss) gain on financial instruments $ 246 $ 13 $ 51 $ 142
Currency swap contract [member]        
Disclosure of net effect of changes in fair value of derivative financial instruments that did not meet hedging criteria for accounting purposes [Line Items]        
Market value (loss) gain on financial instruments (104)   $ (129) 105
Embedded derivatives [member]        
Disclosure of net effect of changes in fair value of derivative financial instruments that did not meet hedging criteria for accounting purposes [Line Items]        
Market value (loss) gain on financial instruments $ 1     $ 5