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General Information - Summary of Consolidated Subsidiaries (Detail) - KRW (₩)
₩ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Jan. 01, 2018
Jan. 01, 2017
Disclosure of subsidiaries [line items]          
Total assets ₩ 32,474,120 ₩ 29,895,721   ₩ 31,252,689 ₩ 30,814,580
Total liabilities 17,815,630 16,712,367   ₩ 17,062,496 ₩ 17,897,638
Operating revenues 23,436,050 23,546,929 ₩ 23,164,202    
Profit (loss) for the year ₩ 719,412 ₩ 546,341 ₩ 831,845    
KT Powertel Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Powertel Co., Ltd. KT Powertel Co., Ltd. KT Powertel Co., Ltd.    
Total assets ₩ 124,064 ₩ 115,125 ₩ 113,725    
Type of Business Trunk radio system business        
Total liabilities ₩ 28,217 18,937 19,899    
Location Korea        
Operating revenues ₩ 65,620 ₩ 69,234 81,390    
Controlling percentage ownership 44.80% 44.80%      
Profit (loss) for the year ₩ (5,545) ₩ 2,112 ₩ 202    
Closing month December        
KT Linkus Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Linkus Co., Ltd. KT Linkus Co., Ltd. KT Linkus Co., Ltd.    
Total assets ₩ 54,147 ₩ 59,344 ₩ 64,318    
Type of Business Public telephone maintenance        
Total liabilities ₩ 44,895 51,516 56,953    
Location Korea        
Operating revenues ₩ 106,337 ₩ 112,043 117,587    
Controlling percentage ownership 92.40% 91.40%      
Profit (loss) for the year ₩ 1,216 ₩ 725 ₩ (3,830)    
Closing month December        
KT Submarine Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Submarine Co., Ltd. KT Submarine Co., Ltd. KT Submarine Co., Ltd.    
Total assets ₩ 130,715 ₩ 142,797 ₩ 156,993    
Type of Business Submarine cable construction and maintenance        
Total liabilities ₩ 27,530 34,056 55,573    
Location Korea        
Operating revenues ₩ 61,652 ₩ 73,985 84,137    
Controlling percentage ownership 39.30% 39.30%      
Profit (loss) for the year ₩ (4,286) ₩ 8,243 ₩ 5,146    
Closing month December        
KT Telecop Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Telecop Co., Ltd. KT Telecop Co., Ltd. KT Telecop Co., Ltd.    
Total assets ₩ 272,492 ₩ 264,353 ₩ 265,553    
Type of Business Security service        
Total liabilities ₩ 140,314 131,633 132,344    
Location Korea        
Operating revenues ₩ 328,262 ₩ 317,591 315,948    
Controlling percentage ownership 86.80% 86.80%      
Profit (loss) for the year ₩ 166 ₩ 2,885 ₩ 143    
Closing month December        
KT Hitel Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Hitel Co., Ltd. KT Hitel Co., Ltd. KT Hitel Co., Ltd.    
Total assets ₩ 272,708 ₩ 258,240 ₩ 249,202    
Type of Business Data communication        
Total liabilities ₩ 66,043 52,943 46,941    
Location Korea        
Operating revenues ₩ 279,117 ₩ 227,884 198,994    
Controlling percentage ownership 67.10% 67.10%      
Profit (loss) for the year ₩ 657 ₩ 3,225 ₩ 4,298    
Closing month December        
KT service bukbu Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Service Bukbu Co., Ltd. KT Service Bukbu Co., Ltd. KT Service Bukbu Co., Ltd.    
Total assets ₩ 30,599 ₩ 29,281 ₩ 32,863    
Type of Business Opening services of fixed line        
Total liabilities ₩ 23,964 22,096 24,580    
Location Korea        
Operating revenues ₩ 195,961 ₩ 194,837 182,952    
Controlling percentage ownership 67.30% 67.30%      
Profit (loss) for the year ₩ (31) ₩ 688 ₩ 694    
Closing month December        
KT service nambu Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Service Nambu Co., Ltd. KT Service Nambu Co., Ltd. KT Service Nambu Co., Ltd.    
Total assets ₩ 37,452 ₩ 36,076 ₩ 32,621    
Type of Business Opening services of fixed line        
Total liabilities ₩ 27,939 26,412 24,282    
Location Korea        
Operating revenues ₩ 230,088 ₩ 232,996 218,602    
Controlling percentage ownership 77.30% 77.30%      
Profit (loss) for the year ₩ 160 ₩ 875 ₩ 772    
Closing month December        
KT Commerce Inc. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Commerce Inc.        
Type of Business B2C, B2B service        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KT Strategic Investment Fund No.1 [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Strategic Investment Fund No.1        
Type of Business Investment fund        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KT Strategic Investment Fund No.2 [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Strategic Investment Fund No.2        
Type of Business Investment fund        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KT Strategic Investment Fund No.3 [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Strategic Investment Fund No.3        
Type of Business Investment fund        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KT strategic investment fund number four [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Strategic Investment Fund No.4        
Type of Business Investment fund        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
BCVP Strategic Investment Fund Number One [member]          
Disclosure of subsidiaries [line items]          
Subsidiary BC-VP Strategic Investment Fund No.1        
Type of Business Investment fund        
Location Korea        
Controlling percentage ownership 100.00%        
Closing month December        
BC Card Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary BC Card Co., Ltd. BC Card Co., Ltd. BC Card Co., Ltd.1    
Total assets ₩ 3,722,379 ₩ 4,048,263 ₩ 3,651,065    
Type of Business Credit card business        
Total liabilities ₩ 2,630,536 2,955,038 2,602,404    
Location Korea        
Operating revenues ₩ 3,551,715 ₩ 3,628,995 3,567,512    
Controlling percentage ownership 69.50% 69.50%      
Profit (loss) for the year ₩ 70,889 ₩ 156,109 ₩ 163,131    
Closing month December        
VP Inc. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary VP Inc.        
Type of Business Payment security service for credit card, others        
Location Korea        
Controlling percentage ownership 50.90% 50.90%      
Closing month December        
H&C Network [member]          
Disclosure of subsidiaries [line items]          
Subsidiary H&C Network H&C Network H&C Network1    
Total assets ₩ 245,841 ₩ 273,856 ₩ 272,110    
Type of Business Call centre for financial sectors        
Total liabilities ₩ 63,188 65,446 80,983    
Location Korea        
Operating revenues ₩ 297,470 ₩ 277,622 266,613    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (15,944) ₩ 16,104 ₩ 14,749    
Closing month December        
BC Card China Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary BC Card China Co., Ltd.        
Type of Business Software development and data processing        
Location China        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
INITECH Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary INITECH Co., Ltd.        
Type of Business Internet banking ASP and security solutions        
Location Korea        
Controlling percentage ownership 58.20% 58.20%      
Closing month December        
Smartro Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary Smartro Co., Ltd.        
Type of Business VAN (Value Added Network) business        
Location Korea        
Controlling percentage ownership 81.10% 81.10%      
Closing month December        
KTDS Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KTDS Co., Ltd. KTDS Co., Ltd. KTDS Co., Ltd.1    
Total assets ₩ 148,675 ₩ 144,922 ₩ 197,970    
Type of Business System integration and maintenance        
Total liabilities ₩ 95,834 93,343 151,644    
Location Korea        
Operating revenues ₩ 434,302 ₩ 459,266 476,379    
Controlling percentage ownership 95.50% 95.50%      
Profit (loss) for the year ₩ 8,586 ₩ 11,584 ₩ 10,838    
Closing month December        
KT M Hows Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT M Hows Co., Ltd. KT M Hows Co., Ltd. KT M Hows Co., Ltd.    
Total assets ₩ 60,197 ₩ 42,738 ₩ 28,539    
Type of Business Mobile marketing        
Total liabilities ₩ 42,386 28,489 18,466    
Location Korea        
Operating revenues ₩ 26,673 ₩ 24,610 19,922    
Controlling percentage ownership 90.00% 90.00%      
Profit (loss) for the year ₩ 3,691 ₩ 4,097 ₩ 2,865    
Closing month December        
KT M&S Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT M&S Co., Ltd. KT M&S Co., Ltd. KT M&S Co., Ltd.    
Total assets ₩ 228,073 ₩ 242,388 ₩ 247,854    
Type of Business PCS distribution        
Total liabilities ₩ 207,740 231,151 227,507    
Location Korea        
Operating revenues ₩ 791,652 ₩ 734,420 724,144    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 11,408 ₩ (9,707) ₩ (12,955)    
Closing month December        
GENIE Music Corporation K T Music Corporation [member]          
Disclosure of subsidiaries [line items]          
Subsidiary GENIE Music Corporation(KT Music Corporation)        
Type of Business Online music production and distribution        
Location Korea        
Controlling percentage ownership 36.00% 42.50%      
Closing month December        
KT MOS Bukbu Co.,Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT MOS Bukbu Co., Ltd.        
Total assets ₩ 14,121        
Type of Business Telecommunication facility maintenance        
Total liabilities ₩ 10,571        
Location Korea        
Operating revenues ₩ 16,543        
Controlling percentage ownership 100.00%        
Profit (loss) for the year ₩ (782)        
Closing month December        
KTMOS Nambu Co.,Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT MOS Nambu Co., Ltd.        
Total assets ₩ 14,313        
Type of Business Telecommunication facility maintenance        
Total liabilities ₩ 8,927        
Location Korea        
Operating revenues ₩ 14,941        
Controlling percentage ownership 98.40%        
Profit (loss) for the year ₩ (2,418)        
Closing month December        
KT Skylife Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Skylife Co., Ltd. KT Skylife Co., Ltd. KT Skylife Co., Ltd.1    
Total assets ₩ 816,001 ₩ 792,893 ₩ 777,948    
Type of Business Satellite broadcasting business        
Total liabilities ₩ 149,841 210,550 231,452    
Location Korea        
Operating revenues ₩ 694,059 ₩ 687,752 668,945    
Controlling percentage ownership 50.30% 50.30%      
Profit (loss) for the year ₩ 52,010 ₩ 57,314 ₩ 68,863    
Closing month December        
Skylife TV Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary Skylife TV Co., Ltd.        
Type of Business TV contents provider        
Location Korea        
Controlling percentage ownership 92.60% 92.60%      
Closing month December        
KT Estate Inc. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Estate Inc. KT Estate Inc. KT Estate Inc.1    
Total assets ₩ 1,695,995 ₩ 1,869,194 ₩ 1,734,729    
Type of Business Residential building development and supply        
Total liabilities ₩ 304,712 502,915 375,341    
Location Korea        
Operating revenues ₩ 569,269 ₩ 428,446 405,417    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 51,854 ₩ 52,416 ₩ 46,815    
Closing month December        
KT AMC Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT AMC Co., Ltd.        
Type of Business Asset management and consulting services        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
NEXR Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary NEXR Co., Ltd.        
Type of Business Cloud system implementation        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KTSB Data service [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KTSB Data service KTSB Data service KTSB Data service    
Total assets ₩ 8,632 ₩ 18,306 ₩ 20,075    
Type of Business Data centre development and related service        
Total liabilities ₩ 523 605 759    
Location Korea        
Operating revenues ₩ 4,627 ₩ 4,950 5,136    
Controlling percentage ownership 51.00% 51.00%      
Profit (loss) for the year ₩ (9,576) ₩ (1,651) ₩ (1,983)    
Closing month December        
KT Sat Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Sat Co., Ltd. KT Sat Co., Ltd. KT Sat Co., Ltd.    
Total assets ₩ 685,926 ₩ 742,391 ₩ 744,653    
Type of Business Satellite communication business        
Total liabilities ₩ 173,513 220,804 253,041    
Location Korea        
Operating revenues ₩ 137,186 ₩ 147,649 144,594    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 4,921 ₩ 29,601 ₩ 36,266    
Closing month December        
Nasmedia Co Ltd [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Nasmedia Co., Ltd. Nasmedia Co., Ltd. Nasmedia Co., Ltd.    
Total assets ₩ 303,112 ₩ 315,967 ₩ 263,925    
Type of Business Online advertisement        
Total liabilities ₩ 161,164 188,197 159,502    
Location Korea        
Operating revenues ₩ 106,805 ₩ 120,667 70,037    
Controlling percentage ownership 42.80% 42.80%      
Profit (loss) for the year ₩ 20,596 ₩ 26,676 ₩ 11,972    
Closing month December        
KT sports [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Sports Co., Ltd KT Sports KT Sports    
Total assets   ₩ 11,131 ₩ 16,925    
Type of Business Management of sports group        
Total liabilities   7,805 13,573    
Location Korea        
Operating revenues   ₩ 53,357 48,476    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year   ₩ (199) ₩ (198)    
Closing month December        
KT music contents fund no.1 [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Music Contents Fund No.1 KT Music Contents Fund No.1 KT Music Contents Fund No.1    
Total assets ₩ 14,092 ₩ 13,804 ₩ 10,592    
Type of Business Music contents investment business        
Total liabilities ₩ 1,035 1,041 331    
Location Korea        
Operating revenues ₩ 559 ₩ 370 349    
Controlling percentage ownership 80.00% 80.00%      
Profit (loss) for the year ₩ 294 ₩ (499) ₩ 103    
Closing month December        
K T Music Contents Fund No.2 [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Music Contents Fund No.2        
Type of Business Music contents investment business        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
KT-Michigan global content fund [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT-Michigan Global Content Fund KT-Michigan Global Content Fund KT-Michigan Global Content Fund    
Total assets ₩ 12,741 ₩ 14,575 ₩ 16,250    
Type of Business Content investment business        
Total liabilities   147 163    
Location Korea        
Operating revenues ₩ 869 ₩ 159 133    
Controlling percentage ownership 88.60% 88.60%      
Profit (loss) for the year ₩ (670) ₩ (426) ₩ (514)    
Closing month December        
Autopion Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Autopion Co., Ltd. Autopion Co., Ltd. Autopion Co., Ltd.    
Total assets ₩ 8,838 ₩ 6,306 ₩ 6,163    
Type of Business Service for information and communication        
Total liabilities ₩ 5,801 3,530 2,794    
Location Korea        
Operating revenues ₩ 12,035 ₩ 6,679 7,772    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 453 ₩ (618) ₩ (409)    
Closing month December        
KTCS Corporation [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KTCS Corporation KTCS Corporation KTCS Corporation1    
Total assets ₩ 350,280 ₩ 348,334 ₩ 322,768    
Type of Business Database and online information provider        
Total liabilities ₩ 188,561 188,764 166,642    
Location Korea        
Operating revenues ₩ 1,019,787 ₩ 968,186 955,050    
Controlling percentage ownership 30.90% 30.90%      
Profit (loss) for the year ₩ 11,401 ₩ 7,385 ₩ 7,892    
Closing month December        
KTIS Corporation [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KTIS Corporation KTIS Corporation KTIS Corporation    
Total assets ₩ 229,246 ₩ 223,818 ₩ 221,176    
Type of Business Database and online information provider        
Total liabilities ₩ 68,997 62,569 63,871    
Location Korea        
Operating revenues ₩ 451,532 ₩ 438,597 436,914    
Controlling percentage ownership 30.10% 30.10%      
Profit (loss) for the year ₩ 7,900 ₩ 8,337 ₩ 9,991    
Closing month December        
KT M mobile [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT M mobile KT M mobile KT M mobile    
Total assets ₩ 146,334 ₩ 93,601 ₩ 131,446    
Type of Business Special category telecommunications operator and sales of communication device        
Total liabilities ₩ 35,335 21,453 20,369    
Location Korea        
Operating revenues ₩ 172,674 ₩ 159,684 112,532    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (10,085) ₩ (38,883) ₩ (40,041)    
Closing month December        
KT Investment Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Investment Co., Ltd. KT Investment Co., Ltd. KT Investment Co., Ltd.1    
Total assets ₩ 74,580 ₩ 54,673 ₩ 39,506    
Type of Business Technology business finance        
Total liabilities ₩ 58,040 38,313 23,123    
Location Korea        
Operating revenues ₩ 8,095 ₩ 8,794 10,130    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 247 ₩ (619) ₩ (1,832)    
Closing month December        
Whowho&Company Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary Whowho&Company Co., Ltd.        
Type of Business Software development and supply        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
PlayD Co., Ltd. (N Search Marketing Co., Ltd.) [member]          
Disclosure of subsidiaries [line items]          
Subsidiary PlayD Co., Ltd. (N Search Marketing Co., Ltd.)        
Type of Business Advertising agency business        
Location Korea        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
Next Connect PFV [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Next connect PFV        
Total assets ₩ 385,769        
Type of Business Residential building development and supply        
Total liabilities ₩ 34,370        
Location Korea        
Operating revenues ₩ 143        
Controlling percentage ownership 100.00%        
Profit (loss) for the year ₩ (12,449)        
Closing month December        
KT Rwanda Networks Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Rwanda Networks Ltd. KT Rwanda Networks Ltd. KT Rwanda Networks Ltd.    
Total assets ₩ 144,129 ₩ 151,359 ₩ 167,112    
Type of Business Network installation and management        
Total liabilities ₩ 162,801 139,561 138,651    
Location Rwanda        
Operating revenues ₩ 15,150 ₩ 15,931 13,435    
Controlling percentage ownership 51.00% 51.00%      
Profit (loss) for the year ₩ (29,238) ₩ (22,762) ₩ (31,455)    
Closing month December        
AOS Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary AOS Ltd. AOS Ltd. AOS Ltd.    
Total assets ₩ 14,018 ₩ 9,437 ₩ 10,025    
Type of Business System integration and maintenance        
Total liabilities ₩ 4,952 4,519 3,179    
Location Rwanda        
Operating revenues ₩ 6,300 ₩ 8,952 14,481    
Controlling percentage ownership 51.00% 51.00%      
Profit (loss) for the year ₩ (680) ₩ (682) ₩ (1,123)    
Closing month December        
KT Belgium [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Belgium KT Belgium KT Belgium    
Total assets ₩ 90,172 ₩ 86,455 ₩ 79,391    
Type of Business Foreign investment business        
Total liabilities ₩ 1 8 7    
Location Belgium        
Operating revenues ₩ 29 ₩ 49      
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (43) ₩ (2) ₩ (67)    
Closing month December        
KT ORS Belgium [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT ORS Belgium KT ORS Belgium KT ORS Belgium    
Total assets ₩ 6,709 ₩ 1,769 ₩ 2,013    
Type of Business Foreign investment business        
Total liabilities ₩ 5 14 23    
Location Belgium        
Operating revenues   ₩ 10      
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (46) ₩ (10) ₩ (46)    
Closing month December        
Korea Telecom Japan Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Korea Telecom Japan Co., Ltd. Korea Telecom Japan Co., Ltd. Korea Telecom Japan Co., Ltd.    
Total assets ₩ 1,326 ₩ 1,554 ₩ 3,592    
Type of Business Foreign telecommunication business        
Total liabilities ₩ 2,910 2,788 5,374    
Location Japan        
Operating revenues ₩ 1,965 ₩ 2,772 5,122    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (126) ₩ 536 ₩ (1,391)    
Closing month December        
KBTO sp.zo.o. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KBTO sp.zo.o. KBTO sp.zo.o. KBTO sp.zo.o.    
Total assets ₩ 1,364 ₩ 3,311 ₩ 1,166    
Type of Business Electronic communication business        
Total liabilities ₩ 217 2,268 2,378    
Location Poland        
Operating revenues ₩ 202 ₩ 67 21    
Controlling percentage ownership 96.20% 94.30%      
Profit (loss) for the year ₩ (3,771) ₩ (3,456) ₩ (2,587)    
Closing month December        
Korea Telecom China Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Korea Telecom China Co., Ltd. Korea Telecom China Co., Ltd. Korea Telecom China Co., Ltd.    
Total assets ₩ 661 ₩ 665 ₩ 532    
Type of Business Foreign telecommunication business        
Total liabilities ₩ 22 32 188    
Location China        
Operating revenues ₩ 681 ₩ 1,030 930    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 10 ₩ 348 ₩ 60    
Closing month December        
KT Dutch B.V. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Dutch B.V. KT Dutch B.V. KT Dutch B.V.    
Total assets ₩ 31,693 ₩ 30,312 ₩ 34,197    
Type of Business Super iMax and East Telecom management        
Total liabilities ₩ 41 50 73    
Location Netherlands        
Operating revenues ₩ 191 ₩ 206 166    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 105 ₩ 169 ₩ 85    
Closing month December        
Super iMax LLC [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Super iMax LLC Super iMax LLC Super iMax LLC    
Total assets ₩ 4,150 ₩ 3,449 ₩ 10,308    
Type of Business Wireless high speed internet business        
Total liabilities ₩ 4,528 4,886 6,734    
Location Uzbekistan        
Operating revenues ₩ 4,845 ₩ 7,314 10,759    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ (424) ₩ (4,584) ₩ (1,802)    
Closing month December        
East Telecom LLC [member]          
Disclosure of subsidiaries [line items]          
Subsidiary East Telecom LLC East Telecom LLC East Telecom LLC    
Total assets ₩ 16,590 ₩ 11,672 ₩ 31,885    
Type of Business Fixed line telecommunication business        
Total liabilities ₩ 14,263 11,748 16,554    
Location Uzbekistan        
Operating revenues ₩ 15,087 ₩ 19,663 27,492    
Controlling percentage ownership 91.00% 91.00%      
Profit (loss) for the year ₩ 2,639 ₩ (9,118) ₩ 3,257    
Closing month December        
Korea Telecom America, Inc. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Korea Telecom America, Inc. Korea Telecom America, Inc. Korea Telecom America, Inc.    
Total assets ₩ 4,218 ₩ 3,694 ₩ 4,464    
Type of Business Foreign telecommunication business        
Total liabilities ₩ 832 791 1,306    
Location USA        
Operating revenues ₩ 7,554 ₩ 6,783 7,113    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 350 ₩ 109 ₩ 181    
Closing month December        
PT. KT Indonesia [member]          
Disclosure of subsidiaries [line items]          
Subsidiary PT. KT Indonesia PT. KT Indonesia PT. KT Indonesia    
Total assets ₩ 8 ₩ 8 ₩ 16    
Type of Business Foreign telecommunication business        
Location Indonesia        
Controlling percentage ownership 99.00% 99.00%      
Profit (loss) for the year   ₩ (6) ₩ (7)    
Closing month December        
PT BC card Asia Pacific [member]          
Disclosure of subsidiaries [line items]          
Subsidiary PT. BC Card Asia Pacific        
Type of Business Software development and supply        
Location Indonesia        
Controlling percentage ownership 99.90% 99.90%      
Closing month December        
KT Hongkong Telecommunications Co., Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Hongkong Telecommunications Co., Ltd. KT Hongkong Telecommunications Co., Ltd. KT Hongkong Telecommunications Co., Ltd.    
Total assets ₩ 3,616 ₩ 2,578 ₩ 1,571    
Type of Business Fixed line communication business        
Total liabilities ₩ 2,143 1,497 956    
Location Hong Kong        
Operating revenues ₩ 9,990 ₩ 7,304 1,568    
Controlling percentage ownership 100.00% 100.00%      
Profit (loss) for the year ₩ 351 ₩ 494 ₩ 120    
Closing month December        
KT Hong kong Limited [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Hong Kong Limited        
Type of Business Foreign investment business        
Location Hong Kong        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
Korea Telecom Singapore Pte.Ltd. [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Korea Telecom Singapore Pte. Ltd.        
Type of Business Foreign investment business        
Location Singapore        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
Texnoprosistem LLP [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Texnoprosistem LLP        
Type of Business Fixed line internet business        
Location Uzbekistan        
Controlling percentage ownership 100.00% 100.00%      
Closing month December        
Nasmedia Thailand Company Limited [member]          
Disclosure of subsidiaries [line items]          
Subsidiary Nasmedia Thailand Company Limited        
Type of Business Internet advertising solution        
Location Thailand        
Controlling percentage ownership 99.90%        
Closing month December        
GENIE Music Corporation(KT Music Corporation) [member]          
Disclosure of subsidiaries [line items]          
Subsidiary GENIE Music Corporation (KT Music Corporation) GENIE Music Corporation(KT Music Corporation) GENIE Music Corporation (KT Music Corporation)    
Total assets ₩ 221,559 ₩ 139,686 ₩ 110,080    
Total liabilities 75,827 48,512 41,953    
Operating revenues 171,314 156,163 111,450    
Profit (loss) for the year ₩ 6,374 ₩ (3,401) ₩ 8,235    
KT Sports Co Ltd [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Sports Co., Ltd.        
Total assets ₩ 9,560        
Total liabilities 6,376        
Operating revenues 55,565        
Profit (loss) for the year ₩ (154)        
KT music contents fund number two [member]          
Disclosure of subsidiaries [line items]          
Subsidiary KT Music Contents Fund No.2 KT Music Contents Fund No.2      
Total assets ₩ 7,629 ₩ 7,500      
Total liabilities 281 11      
Operating revenues 150        
Profit (loss) for the year ₩ (142) ₩ (11)      
KT Innoedu Co., Ltd. [Member]          
Disclosure of subsidiaries [line items]          
Subsidiary     KT Innoedu Co., Ltd.    
Total assets     ₩ 6,477    
Total liabilities     7,259    
Operating revenues     15,599    
Profit (loss) for the year     ₩ 103    
NgeneBio [member]          
Disclosure of subsidiaries [line items]          
Subsidiary     NgeneBio    
Total assets     ₩ 6,361    
Total liabilities     4,733    
Operating revenues     244    
Profit (loss) for the year     ₩ (1,833)