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Defined benefit plans -Summary of sensitivity analysis for actuarial assumptions (Details) (Parenthetical) - KRW (₩)
₩ in Millions
Dec. 31, 2026
Dec. 31, 2025
Dec. 31, 2024
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Defined benefit plan expected future benefit payments Year 2026 ₩ 161,400    
Actuarial assumption of discount rates [member]      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Percentage of reasonably possible increase in actuarial assumption   1.00% 1.00%
Actuarial assumption of expected rates of salary increases [member]      
Disclosure of sensitivity analysis for actuarial assumptions [line items]      
Percentage of reasonably possible decrease in actuarial assumption   1.00% 1.00%