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Property and Equipment - Summary of Estimated Useful Lives of Property and Equipment (Detail)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Cable and wire facilities [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 5 years 5 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 equipment [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Central equipment [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 15 years 15 years
Network facilities [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Network facilities [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 15 years 15 years
Buildings [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 25 years 25 years
Buildings [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 50 years 50 years
Vehicles, 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, 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 15 years 7 years
Land improvements [Member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 10 years 10 years
IT systems and platforms [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
IT systems and platforms [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 5 years 5 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
Security platforms [Member] | Bottom of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 3 years 3 years
Security platforms [Member] | Top of range [member]    
Disclosure Of Property Plant And Equipment [Line Items]    
Estimated useful lives of assets 5 years 5 years