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Trade Accounts Receivable, Net - Summary of Changes in Valuation of Caption Allowance for Doubtful Accounts (Detail) - MXN ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of financial assets [abstract]      
Allowances for doubtful accounts at beginning of period $ 2,196 $ 2,152 $ 1,856
Charged to selling expenses 252 556 434
Additions through business combinations 141 0 0
Deductions (449) (867) (276)
Foreign currency translation effects 5 355 138
Allowances for doubtful accounts at end of period $ 2,145 $ 2,196 $ 2,152