v3.26.1
Operating Segments - Summary of Disaggregation of Operating Revenue (Detail) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue ₩ 17,099,213 ₩ 17,940,609 ₩ 17,608,511
Goods and Services transferred at a point in time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 1,446,361 1,616,027 1,546,998
Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 15,652,852 16,324,582 16,061,513
Cellular revenue [member] | Goods [member] | Goods and Services transferred at a point in time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 1,034,695 1,078,673 993,919
Cellular revenue [member] | Wireless service [member] | Bottom of range [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 454,143    
Cellular revenue [member] | Wireless service [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 9,715,601 10,401,565 10,328,980
Cellular revenue [member] | Cellular interconnection [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 369,870 400,516 432,660
Cellular revenue [member] | Other [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 1,432,377 1,437,459 1,367,607
Fixed-line telecommunication revenue [member] | Goods [member] | Goods and Services transferred at a point in time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 86,249 68,836 93,174
Fixed-line telecommunication revenue [member] | Cellular interconnection [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 12,384 14,014 15,804
Fixed-line telecommunication revenue [member] | Fixedline Service [Member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 142,500 156,453 147,669
Fixed-line telecommunication revenue [member] | Internet protocol television [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 1,806,840 1,837,199 1,837,209
Fixed-line telecommunication revenue [member] | International calls [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 200,860 213,745 190,872
Fixed-line telecommunication revenue [member] | Internet service and miscellaneous [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 1,942,280 1,785,165 1,643,292
Other revenue [member] | Other [member] | Goods and Services transferred at a point in time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue 325,417 468,518 459,905
Other revenue [member] | Miscellaneous [member] | Goods and Services transferred over time [member]      
Disclosure of disaggregation of revenue from contracts with customers [line items]      
Revenue ₩ 30,140 ₩ 78,466 ₩ 97,420