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Lease Arrangements - Additional Information (Details) - Taiwan [Member]
 12 Months Ended
Dec. 31, 2019
Bottom of Range [Member] | Handsets Base Stations [Member]  
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]  
Lease Term 1 year
Bottom of Range [Member] | Offices, Server rooms and Stores [Member]  
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]  
Lease Term 1 year
Top of Range [Member] | Handsets Base Stations [Member]  
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]  
Lease Term 20 years
Top of Range [Member] | Offices, Server rooms and Stores [Member]  
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]  
Lease Term 30 years