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Financial Instruments - Disclosure of Net Effect of Expired Contracts Did Not Meet Hedging Criteria for Accounting Purposes (Detail)
$ in Millions
12 Months Ended
Dec. 31, 2017
MXN ($)
Derivative financial instruments did not meet hedging criteria [member] | Cross-currency swaps [member] | Market value gain on financial instruments [member]  
Disclosure of detailed information about hedges [line items]  
Net effects derivative contracts hedging criteria $ (438)