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Financial Instruments - Disclosure of Net Effects of Expired Contracts Met Hedging Criteria (Detail) - Derivative contracts that met hedging criteria [Member] - MXN ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Cross-currency swaps [member] | Interest expense [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria $ 2,102   $ 2,595
Cross-currency swaps [member] | Foreign exchange [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria     (10,911)
Forward agreements to purchase foreign currency [member] | Foreign exchange [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria (40) $ 160 (180)
Forward agreements to purchase foreign currency [member] | Cost of goods sold [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria 689 (45) (523)
Commodity price contracts [Member] | Cost of goods sold [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria $ (6) $ (241) 619
Options to purchase foreign currency [Member] | Cost of goods sold [Member]      
Disclosure of detailed information about hedges [line items]      
Net effects derivative contracts hedging criteria     $ (21)