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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]      
Plan assets including securities   $ 114  
Current service costs included in cost of goods sold, administration and selling expenses $ 408 $ 359 $ 343
Mexican subsidiaries [member]      
Disclosure of defined benefit plans [line items]      
Plan asset investment for related parties, percentage 10.00%    
Bottom of range [member] | Mexican Federal Government instruments [member]      
Disclosure of defined benefit plans [line items]      
Fund assets, percentage 30.00%    
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%