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Trade Receivable, Net - Summary of Changes in Allowance for Expected Credit Losses (Detail) - MXN ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Allowance for Doubtful Accounts [Roll Forward]      
Balance at the beginning of the year $ 493 $ 595 $ 468
Allowance for the year 119 314 153
Charges and write-offs of uncollectible accounts (29) (397) 23
Added in business combinations 0 4 1
Effects of changes in foreign exchange rates (68) (23) (55)
Balance at the end of the year 515 493 595
Philippines      
Allowance for Doubtful Accounts [Roll Forward]      
Effect of Philippines 0 0 (82)
Adoption of IFRS 9      
Allowance for Doubtful Accounts [Roll Forward]      
Effect of adoption of IFRS 9 $ 0 $ 0 $ 87