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Basis of Preparation of the Consolidated Financial Statements and Summary of Significant Accounting Policies and Practices - Additional Information (Detail)
R$ in Thousands, $ in Millions
 12 Months Ended
Dec. 31, 2017
MXN ($)
Segment
Supplier
Dec. 31, 2017
BRL (R$)
Segment
Supplier
Dec. 31, 2016
MXN ($)
Dec. 31, 2015
MXN ($)
Apr. 26, 2018
Dec. 31, 2017
USD ($)
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Cumulative translation (loss) gain $ (73,261,794,000)   $ (45,137,571,000)     $ (3,703)
Impairment losses on goodwill 0   0 $ 0    
Borrowing costs capitalised 2,875,034,000   2,861,307,000 3,524,841,000    
Impairment losses 0   0 0    
Potentially reversible assets for an estimated gross book value 20,637,743,000 R$ 3,450,100        
Impairment losses on intangibles $ 0   0 0    
Description of estimation of impairment cash-generating unit In the estimation of impairments, the Company uses the strategic plans established for the separate cash-generating units to which the assets are assigned. Such strategic plans generally cover a period from 3 to 5 years. For longer periods, beginning in the fifth year, projections are based on such strategic plans while applying a constant or declining expected growth rate. In the estimation of impairments, the Company uses the strategic plans established for the separate cash-generating units to which the assets are assigned. Such strategic plans generally cover a period from 3 to 5 years. For longer periods, beginning in the fifth year, projections are based on such strategic plans while applying a constant or declining expected growth rate.        
Percentage of sensitivity analysis for increase in capital expenditures 5.00% 5.00%        
Adjustments of sensitivity analysis long-life assets $ 2,386,782,000          
Increase in weighted average cost of capital basis 0.50% 0.50%        
Adjustments for assumption of weighted average cost of capital $ 3,517,584,000          
Monthly contributions to pension fund 17.50% 17.50%        
Percentage of employee profit sharing based on individual company taxable income 10.00% 10.00%        
Advertising expenses $ 28,718,563,000   28,180,538,000 $ 24,673,557,000    
Increase (decrease) in interest expense $ 697,884,899,000   $ 707,801,403,000      
Concentration risk percentage 10.00% 10.00%        
Number of segments | Segment 0 0        
Foreign subsidiaries [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Consolidated operating revenues 74.00% 74.00% 72.00% 69.00%    
Percentage of operating revenue as percentage of total assets 81.00% 81.00% 83.00%      
Cost of sales [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Employee benefits expense $ 48,696,331,000   $ 46,759,415,000 $ 41,366,183,000    
Commercial, administrative and general expenses [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Employee benefits expense $ 66,920,537,000   $ 63,691,855,000 $ 58,977,212,000    
Cellular equipment [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Percentage of purchases made from key suppliers and sellers 69.00% 69.00% 73.00% 67.00%    
Number of key suppliers and sellers | Supplier 3 3        
Interest rate risk [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Increase in basis points 1.00% 1.00%        
Increase in net interest expense $ 8,221,411,000          
Increase (decrease) in interest expense $ (8,002,209,000)          
Currency risk [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Fluctuation in exchange rates 5.00%         5.00%
Increase (decrease) in interest expense $ 697,884,899,000          
Increase (decrease) through changes in foreign exchange rates, regulatory deferral account credit balances 36,079,857,000          
Increase (decrease) through changes in discount rates, regulatory deferral account credit balances $ (33,821,548,000)          
Increase/(decrease) in exchange rates 5.00% 5.00%        
U.S.A. [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Closing exchange rate         18.8139  
U.S.A. [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Closing exchange rate 19.7867   20.7314     19.7867
Cumulative translation adjustment [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Cumulative translation (loss) gain $ 7,866,158,000   $ 29,549,491,000      
Licenses and rights of use [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Intangibles useful life Licenses are amortized when the Company does not have a basis to conclude that they are indefinite lived. Licenses are amortized using the straight-line method over a period ranging from 3 to 30 years, which represents the usage period of the assets. Licenses are amortized when the Company does not have a basis to conclude that they are indefinite lived. Licenses are amortized using the straight-line method over a period ranging from 3 to 30 years, which represents the usage period of the assets.        
Licenses and rights of use [member] | Bottom of range [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Estimated useful lives 3 years 3 years        
Licenses and rights of use [member] | Top of range [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Estimated useful lives 30 years 30 years        
Trademarks [member] | Bottom of range [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Estimated useful lives 1 year 1 year        
Trademarks [member] | Top of range [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Estimated useful lives 10 years 10 years        
Customer relationships [member]            
Disclosure of basis of preparation of consolidated financial statements and summary of significant accounting policies and practices [line items]            
Intangibles useful life Amortized on a 5 year period. Amortized on a 5 year period.        
Estimated useful lives 5 years 5 years