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Post-Employment and Other Non-current Employee Benefits - Additional Information (Detail) - MXN ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of defined benefit plans [line items]      
Service costs included in cost of goods sold, administration and selling expenses $ 285 $ 190 $ 192
Actuarial assumption of discount rates [member]      
Disclosure of defined benefit plans [line items]      
Impact on absolute terms of variation in the assumptions on net defined benefit liability   0.50%  
Mexican Federal Government Instruments [member]      
Disclosure of defined benefit plans [line items]      
Percentage of fund assets 30.00%    
Subsidiaries [member]      
Disclosure of defined benefit plans [line items]      
Percentage of plan asset investment for related parties 10.00%