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Related Parties - Summary of Transactions with Related Parties (Parenthetical) (Detail) - MXN ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure of transactions between related parties [line items]      
Materials purchased from subsidiaries $ 5,312,845 $ 6,809,244 $ 5,622,791
Grupo Carso, SAB de CV [member]      
Disclosure of transactions between related parties [line items]      
Network maintenance service cost 203,013 956,132 778,191
Associates [member]      
Disclosure of transactions between related parties [line items]      
Software service expense 13,490 16,161 13,784
Seguros Inbursa SA and Fianzas Guardiana Inbursa, SA [member]      
Disclosure of transactions between related parties [line items]      
Insurance premium $ 2,713,370 $ 2,623,795 $ 2,541,703