XML 136 R121.htm IDEA: XBRL DOCUMENT v3.8.0.1
Investments in Associates and Joint Ventures - Summary of Details of Associates (Detail)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Disclosure of associates [line items]    
Date of financial statements --12-31  
K Bank Inc. [member]    
Disclosure of associates [line items]    
Percentage of ownership 10.00%  
Location Korea  
Date of financial statements --12-31  
Korea Information & Technology Fund [member]    
Disclosure of associates [line items]    
Percentage of ownership 33.30% 33.30%
Location Korea  
Date of financial statements --12-31  
KT-SB Venture Investment [member]    
Disclosure of associates [line items]    
Percentage of ownership 50.00% 50.00%
Location Korea  
Date of financial statements --12-31  
Mongolian Telecommunications [Member]    
Disclosure of associates [line items]    
Percentage of ownership   40.00%
Location Mongolia  
Date of financial statements --12-31  
KT Wibro Infra Co., Ltd. [member]    
Disclosure of associates [line items]    
Percentage of ownership   26.20%
Location Korea  
Date of financial statements --12-31  
KT-IBKC future investment fund [member]    
Disclosure of associates [line items]    
Percentage of ownership 50.00% 50.00%
Location Korea  
Date of financial statements --12-31  
KT-CKP New Media Investment Fund [member]    
Disclosure of associates [line items]    
Percentage of ownership 49.70% 49.70%
Location Korea  
Date of financial statements --12-31