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Income Taxes - Schedule of Changes in Balance of Tax Loss Carryforwards (Detail) - MXN ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Major components of tax expense (income) [abstract]    
Balance at beginning of the year $ 27,452 $ 16,463
Reserved   (2)
Additions 5,673 6,349
Usage of tax losses (3,157) (168)
Translation effect of beginning balances (481) 4,810
Balance at end of the year $ 29,487 $ 27,452