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Significant Accounting Policies - Summary of Amortization of Intangible Assets With Limited Useful Life (Detail)
 12 Months Ended
Dec. 31, 2020
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 3 years
Development costs [member] | Bottom of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 5 years
Development costs [member] | Top of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 6 years
Software [member] | Bottom of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 4 years
Software [member] | Top of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 6 years
Frequency usage rights [member] | Bottom of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 5 years
Frequency usage rights [member] | Top of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 10 years
Others [member] | Bottom of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 1 year
Others [member] | Top of range [member]  
Disclosure of detailed information about intangible assets [line items]  
Estimated Useful Life 50 years