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Property and Equipment - Summary of Estimated Useful Lives of Property and Equipment (Detail)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Cable and wire facilities [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 10 years 10 years
Cable and wire facilities [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 15 years 15 years
Central office equipment [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 2 years 2 years
Central office equipment [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 15 years 15 years
Cellular facilities [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Cellular facilities [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 10 years 10 years
Building [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 25 years 25 years
Building [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 50 years 50 years
Vehicles, aircraft, furniture and other network equipment [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Vehicles, aircraft, furniture and other network equipment [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 15 years 15 years
Information origination and termination equipment [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Information origination and termination equipment [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 7 years 7 years
Leasehold improvements [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Leasehold improvements [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 10 years 10 years
Land improvements [Member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 10 years 10 years