KT (KT) 20-F 30 Apr 18 2017 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2017shares
Document - Document and Entity Information [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	KT
Entity Registrant Name	KT Corporation
Entity Central Index Key	892,450
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	245,097,055

Consolidated Statements of Fina

Consolidated Statements of Financial Position - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	₩ 1,928,182	₩ 2,900,311
Trade and other receivables, net	5,814,283	5,327,352
Other financial assets	972,631	720,555
Current income tax assets	9,030	2,079
Inventories, net	642,027	454,588
Current assets held for sale	7,230
Other current assets	304,860	311,135
Total current assets	9,678,243	9,716,020
Non-current assets
Trade and other receivables, net	828,832	709,011
Other financial assets	754,992	664,726
Property, plant and equipment, net	13,562,319	14,312,111
Investment properties, net	1,189,531	1,148,044
Intangible assets, net	2,632,704	3,022,803
Investments in associates and joint ventures	279,431	284,075
Deferred income tax assets	712,222	701,409
Other non-current assets	107,165	106,099
Total non-current assets	20,067,196	20,948,278
Total assets	29,745,439	30,664,298
Current liabilities
Trade and other payables	7,424,134	7,139,771
Borrowings	1,573,474	1,820,001
Other financial liabilities	37,223	233
Current income tax liabilities	68,880	88,739
Provisions	78,172	96,485
Deferred revenue	17,906	35,617
Other current liabilities	258,315	342,291
Total current liabilities	9,458,104	9,523,137
Non-current liabilities
Trade and other payables	1,001,369	1,188,311
Borrowings	5,110,188	6,300,790
Other financial liabilities	149,267	108,431
Defined benefit liabilities, net	395,079	378,404
Provisions	124,858	100,694
Deferred revenue	91,698	85,372
Deferred income tax liabilities	128,462	137,680
Other non-current liabilities	237,284	58,761
Total non-current liabilities	7,238,205	8,358,443
Total liabilities	16,696,309	17,881,580
Equity
Share capital	1,564,499	1,564,499
Share premium	1,440,258	1,440,258
Retained earnings	9,826,926	9,644,483
Accumulated other comprehensive income	30,985	(1,432)
Other components of equity	(1,205,302)	(1,217,934)
Equity attributable to owners of the Controlling Company	11,657,366	11,429,874
Non-controlling interest	1,391,764	1,352,844
Total equity	13,049,130	12,782,718
Total liabilities and equity	₩ 29,745,439	₩ 30,664,298

Consolidated Statements of Oper

Consolidated Statements of Operations - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit or loss [abstract]
Operating revenue	₩ 23,546,929	₩ 23,120,878	₩ 22,699,856
Revenue	23,259,541	22,755,006	22,211,673
Others	287,388	365,872	488,183
Operating expenses	22,477,837	21,781,098	21,622,788
Operating profit	1,069,092	1,339,780	1,077,068
Finance income	406,328	296,139	272,860
Finance costs	(644,531)	(515,087)	(645,331)
Share of net profits of associates and joint venture	(13,892)	2,599	6,144
Profit from continuing operations before income tax	816,997	1,123,431	710,741
Income tax expense	270,656	328,314	227,131
Profit from continuing operations	546,341	795,117	483,610
Profit from discontinued operations			141,075
Profit for the year	546,341	795,117	624,685
Profit for the year attributable to:
Profit (loss) for the year attributable to Owners of the Controlling Company	461,559	708,362	546,361
Profit from continuing operations	461,559	708,362	404,045
Profit from discontinued operations			142,316
Profit (loss) for the year attributable to Non-controlling interest	84,782	86,755	78,324
Profit from continuing operations	84,782	86,755	79,565
Loss from discontinued operations			(1,241)
Profit for the year	₩ 546,341	₩ 795,117	₩ 624,685
Earnings per share attributable to the equity holders of the Controlling Company during the year (in Korean won):
Basic earnings per share	₩ 1,884	₩ 2,893	₩ 2,231
From continuing operations	1,884	2,893	1,650
From discontinued operations			581
Diluted earnings per share	1,883	2,891	2,231
From continuing operations	₩ 1,883	₩ 2,891	1,650
From discontinued operations			₩ 581

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of comprehensive income [abstract]
Profit for the year	₩ 546,341	₩ 795,117	₩ 624,685
Other comprehensive income Items that will not be reclassified to profit or loss:
Remeasurements of the net defined benefit liability	(83,962)	4,213	(37,872)
Shares of remeasurement gain (loss) of associates and joint ventures	(115)	116	(2,407)
Other comprehensive income, Items that may be subsequently reclassified to profit or loss:
Changes in value of available-for-sale financial assets	51,235	10,925	47,381
Other comprehensive income from available-for sale financial assets reclassified to loss	(55,450)	(3,840)	(83,397)
Net gain (loss) on cash flow hedges	(111,083)	64,796	111,914
Other comprehensive income (loss) from cash flow hedges reclassified to gain (loss)	141,929	(75,871)	(97,962)
Shares of other comprehensive income (loss) from associates and joint ventures	10,280	(602)	(1,608)
Exchange differences on translation of foreign operations	(21,122)	(5,407)	(4,884)
Total other comprehensive loss	(68,288)	(5,670)	(68,835)
Total comprehensive income for the year	478,053	789,447	555,850
Total comprehensive income for the year attributable to:
Owners of the Controlling Company	413,149	701,685	495,139
Non-controlling interest	64,904	87,762	60,711
Total comprehensive income for the year	₩ 478,053	₩ 789,447	₩ 555,850

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - KRW (₩) ₩ in Millions	Total	Share capital [member]	Share premium [member]	Retained earnings [member]	Accumulated other comprehensive income [member]	Other components of equity [member]	Total attributable to owners of the Controlling Company [member]	Non-controlling interest [member]
Beginning balance at Dec. 31, 2014	₩ 11,787,557	₩ 1,564,499	₩ 1,440,258	₩ 8,568,399	₩ 25,790	₩ (1,260,709)	₩ 10,338,237	₩ 1,449,320
Comprehensive income
Profit for the year	624,685			546,361			546,361	78,324
Changes in value of available-for-sale financial assets	(36,016)				(24,310)		(24,310)	(11,706)
Remeasurements of net defined benefit liability	(37,872)			(37,914)			(37,914)	42
Valuation gains (losses) on cashflow hedge	13,952				13,924		13,924	28
Shares of other comprehensive income (losses) of joint ventures and associates	(1,608)				(1,357)		(1,357)	(251)
Shares of remeasurement gain (loss) of associates and joint ventures	(2,407)			(2,109)			(2,109)	(298)
Exchange differences on translation of foreign operations	(4,884)				(177)		(177)	(4,707)
Total comprehensive income for the year	555,850			506,338	(11,920)		494,418	61,432
Transactions with equity holders
Dividends paid to non-controlling interest of subsidiaries	(41,575)							(41,575)
Changes in consolidation scope	(154,188)							(154,188)
Change in ownership interest in subsidiaries	(269)					(2,968)	(2,968)	2,699
Appropriation of loss on disposal of treasury stock				(24,766)		24,766
Others	8,756					6,048	6,048	2,708
Subtotal	(187,276)			(24,766)		27,846	3,080	(190,356)
Ending balance at Dec. 31, 2015	12,156,131	1,564,499	1,440,258	9,049,971	13,870	(1,232,863)	10,835,735	1,320,396
Comprehensive income
Profit for the year	795,117			708,362			708,362	86,755
Changes in value of available-for-sale financial assets	7,085				1,691		1,691	5,394
Remeasurements of net defined benefit liability	4,213			8,531			8,531	(4,318)
Valuation gains (losses) on cashflow hedge	(11,075)				(11,075)		(11,075)
Shares of other comprehensive income (losses) of joint ventures and associates	(602)				(571)		(571)	(31)
Shares of remeasurement gain (loss) of associates and joint ventures	116			94			94	22
Exchange differences on translation of foreign operations	(5,407)				(5,347)		(5,347)	(60)
Total comprehensive income for the year	789,447			716,987	(15,302)		701,685	87,762
Transactions with equity holders
Dividends paid by the Controlling Company	(122,425)			(122,425)			(122,425)
Dividends paid to non-controlling interest of subsidiaries	(61,674)							(61,674)
Changes in consolidation scope	(4,181)					11,369	11,369	(15,550)
Change in ownership interest in subsidiaries				(50)		50
Appropriation of loss on disposal of treasury stock	21,769							21,769
Others	3,651					3,510	3,510	141
Subtotal	(162,860)			(122,475)		14,929	(107,546)	(55,314)
Ending balance at Dec. 31, 2016	12,782,718	1,564,499	1,440,258	9,644,483	(1,432)	(1,217,934)	11,429,874	1,352,844
Comprehensive income
Profit for the year	546,341			461,559			461,559	84,782
Changes in value of available-for-sale financial assets	(4,215)				(1,433)		(1,433)	(2,782)
Remeasurements of net defined benefit liability	(83,962)			(80,711)			(80,711)	(3,251)
Valuation gains (losses) on cashflow hedge	30,846				30,846		30,846
Shares of other comprehensive income (losses) of joint ventures and associates	10,280				10,148		10,148	132
Shares of remeasurement gain (loss) of associates and joint ventures	(115)			(116)			(116)	1
Exchange differences on translation of foreign operations	(21,122)				(7,144)		(7,144)	(13,978)
Total comprehensive income for the year	478,053			380,732	32,417		413,149	64,904
Transactions with equity holders
Dividends paid by the Controlling Company	(195,977)			(195,977)			(195,977)
Dividends paid to non-controlling interest of subsidiaries	(47,162)							(47,162)
Changes in consolidation scope	250							250
Change in ownership interest in subsidiaries	26,683					5,441	5,441	21,242
Appropriation of loss on disposal of treasury stock				(2,312)		2,312
Others	4,565					4,879	4,879	(314)
Subtotal	(211,641)			(198,289)		12,632	(185,657)	(25,984)
Ending balance at Dec. 31, 2017	₩ 13,049,130	₩ 1,564,499	₩ 1,440,258	₩ 9,826,926	₩ 30,985	₩ (1,205,302)	₩ 11,657,366	₩ 1,391,764

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Cash generated from operations	₩ 4,318,884	₩ 5,202,520	₩ 4,579,260
Interest paid	(252,405)	(372,525)	(436,363)
Interest received	93,769	104,679	128,422
Dividends received	10,843	10,824	35,768
Income tax paid	(293,342)	(174,748)	(77,122)
Net cash inflow from operating activities	3,877,749	4,770,750	4,229,965
Cash flows from investing activities
Collection of loans	55,190	47,887	38,856
Loans granted	(59,800)	(57,400)	(79,136)
Disposal of derivatives			176,681
Disposal of available-for-sale financial assets	146,429	35,791	243,125
Acquisition of available-for-sale financial assets	(89,027)	(44,302)	(99,111)
Disposal of investments in associates and joint ventures	59,818	11,074	42,946
Acquisition of investments in associates and joint ventures	(41,780)	(38,675)	(12,238)
Disposal of current and non-current financial instruments	645,686	293,283	363,260
Acquisition of current and non-current financial instruments	(1,231,917)	(597,345)	(341,373)
Disposal of property and equipment, and investment properties	68,229	93,401	28,303
Acquisition of property and equipment, and investment properties	(2,442,223)	(2,764,346)	(3,115,728)
Disposal of intangible assets	22,680	17,891	25,841
Acquisition of intangible assets	(613,556)	(455,763)	(399,377)
Increase in cash due to exclusion from consolidation scope			741,834
Cash inflow(outflow) from changes in scope of consolidation	(2,974)	(26,454)	(15,751)
Net cash outflow from investing activities	(3,483,245)	(3,484,958)	(2,401,868)
Cash flows from financing activities
Proceeds from borrowings and debentures	616,257	1,122,898	5,675,302
Repayments of borrowings and debentures	(1,780,174)	(1,768,768)	(6,648,177)
Settlement of derivative assets and liabilities, net	71,370	(33,199)	(3,371)
Cash inflow from consolidated capital transactions	27,261	800
Cash outflow from consolidated capital transactions	(300)	(5,140)
Cash inflow from other financing activities	16,962
Dividends paid to shareholders	(243,140)	(184,099)	(41,575)
Decrease in finance leases liabilities	(71,735)	(75,763)	(146,175)
Net cash outflow from financing activities	(1,363,499)	(943,271)	(1,163,996)
Effect of exchange rate change on cash and cash equivalents	(3,134)	(1,674)	6,700
Net increase (decrease) in cash and cash equivalents	(972,129)	340,847	670,801
Cash and cash equivalents, Beginning of the year	2,900,311	2,559,464	1,888,663
Cash and cash equivalents, End of the year	₩ 1,928,182	₩ 2,900,311	₩ 2,559,464

General Information

General Information	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
General Information	1. General Information The consolidated financial statements include the accounts of KT Corporation, which is the controlling company as defined under IFRS 10, Consolidated Financial Statements, and its 59 controlled subsidiaries as described in Note 1.2 (collectively referred to as the “Group”). The Controlling Company KT Corporation (the “Controlling Company”) commenced operations on January 1, 1982, when it spun off from the Korea Communications Commission (formerly the Korean Ministry of Information and Communications) to provide telephone services and to engage in the development of advanced communications services under the Act of Telecommunications of Korea. The headquarters are located in Seongnam City, Gyeonggi Province, Republic of Korea, and the address of its registered head office is 90, Buljeong-ro, Bundang-gu, On October 1, 1997, upon the announcement of the Government-Investment Enterprises Management Basic Act and the Privatization Law, the Controlling Company became a government-funded institution under the Commercial Code of Korea. On December 23, 1998, the Controlling Company’s shares were listed on the Korea Exchange. On May 29, 1999, the Controlling Company issued 24,282,195 additional shares and issued American Depository Shares (ADS), representing new shares and 20,813,311 government-owned shares, at the New York Stock Exchange. On July 2, 2001, the additional ADS representing 55,502,161 government-owned shares were issued at the New York Stock Exchange. In 2002, the Controlling Company acquired the entire government-owned shares in accordance with the Korean government’s privatization plan. As of the end of the reporting period, the Korean government does not own any share in the Controlling Company. Consolidated Subsidiaries The consolidated subsidiaries as of December 31, 2016 and 2017, are as follows: Controlling percentage 1 Subsidiary Type of Business Location December 31, December 31, Closing KT Powertel Co., Ltd. 2 Trunk radio system business Korea 44.8% 44.8% December KT Linkus Co., Ltd. Public telephone maintenance Korea 91.4% 91.4% December KT Submarine Co., Ltd. 2,3 Submarine cable construction and maintenance Korea 39.3% 39.3% December KT Telecop Co., Ltd. Security service Korea 86.8% 86.8% December KT Hitel Co., Ltd. Data communication Korea 67.1% 67.1% December KT Service Bukbu Co., Ltd. Opening services of fixed line Korea 67.3% 67.3% December KT Service Nambu Co., Ltd. Opening services of fixed line Korea 77.3% 77.3% December KT Commerce Inc. B2C, B2B service Korea 100.0% 100.0% December KT New Business Fund No.1 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.1 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.2 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.3 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.4 Investment fund Korea — 100.0% December BC Card Co., Ltd. Credit card business Korea 69.5% 69.5% December VP Inc. Payment security service for credit card, others Korea 50.9% 50.9% December H&C Network Call centre for financial sectors Korea 100.0% 100.0% December BC Card China Co., Ltd. Software development and data processing China 100.0% 100.0% December INITECH Co., Ltd. 4 Internet banking ASP and security solutions Korea 58.2% 58.2% December Smartro Co., Ltd. VAN (Value Added Network) business Korea 81.1% 81.1% December KTDS Co., Ltd. 4 System integration and maintenance Korea 95.5% 95.5% December KT M Hows Co., Ltd. Mobile marketing Korea 90.0% 90.0% December KT M&S Co., Ltd. PCS distribution Korea 100.0% 100.0% December GENIE Music Corporation(KT Music Corporation) 2 Online music production and distribution Korea 49.9% 42.5% December KT Skylife Co., Ltd. 4 Satellite broadcasting business Korea 50.3% 50.3% December Skylife TV Co., Ltd. TV contents provider Korea 92.6% 92.6% December KT Estate Inc. Residential building development and supply Korea 100.0% 100.0% December KT AMC Co., Ltd. Asset management and consulting services Korea 100.0% 100.0% December NEXR Co., Ltd. Cloud system implementation Korea 100.0% 100.0% December KTSB Data service Data centre development and related service Korea 51.0% 51.0% December KT Sat Co., Ltd. Satellite communication business Korea 100.0% 100.0% December KT Innoedu Co E-learning business Korea 96.8% — December Nasmedia, Inc. 3 Online advertisement Korea 42.8% 42.8% December KT Sports Management of sports group Korea 100.0% 100.0% December KT Music Contents Fund No.1 Music contents investment business Korea 80.0% 80.0% December KT Music Contents Fund No.2 Music contents investment business Korea — 100.0% December KT-Michigan Content investment business Korea 88.6% 88.6% December Autopion Co., Ltd. Service for information and communication Korea 100.0% 100.0% December KTCS Corporation 2,4 Database and online information provider Korea 30.9% 30.9% December KTIS Corporation 2,4 Database and online information provider Korea 30.1% 30.1% December KT M mobile Special category telecommunications operator and sales of communication device Korea 100.0% 100.0% December KT Investment Co., Ltd. Technology business finance Korea 100.0% 100.0% December NgenBio Medicine and Pharmacy development business Belgium 49.8% — December Whowho&Company Co., Ltd. Software development and supply Korea 100.0% 100.0% December PlayD Co., Ltd. (N Search Marketing Co., Ltd.) Advertising agency business Korea 100.0% 100.0% December KT Rwanda Networks Ltd. Network installation and management Rwanda 51.0% 51.0% December AOS Ltd. System integration and maintenance Rwanda 51.0% 51.0% December KT Belgium Foreign investment business Belgium 100.0% 100.0% December KT ORS Belgium Foreign investment business Belgium 100.0% 100.0% December Korea Telecom Japan Co., Ltd. Foreign telecommunication business Japan 100.0% 100.0% December KBTO sp.zo.o. Electronic communication business Poland 75.0% 94.0% December Korea Telecom China Co., Ltd. Foreign telecommunication business China 100.0% 100.0% December KT Dutch B.V Super iMax and East Telecom management Netherlands 100.0% 100.0% December Super iMax LLC Wireless high speed internet business Uzbekistan 100.0% 100.0% December East Telecom LLC Fixed line telecommunication business Uzbekistan 91.0% 91.0% December Korea Telecom America, Inc. Foreign telecommunication business USA 100.0% 100.0% December PT. KT Indonesia Foreign telecommunication business Indonesia 99.0% 99.0% December PT. BC Card Asia Pacific Software development and supply Indonesia 99.9% 99.9% December KT Hongkong Telecommunications Co., Ltd. Fixed line communication business Hong Kong 100.0% 100.0% December KT Hong kong Limited Foreign investment business Hong Kong 100.0% 100.0% December Korea Telecom Singapore Pte.Ltd. Foreign investment business Singapore 100.0% 100.0% December Texnoprosistem LLP. Fixed line internet business Uzbekistan 100.0% 100.0% December 1 Sum of the ownership interests owned by the Controlling Company and subsidiaries. 2 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company can exercise the majority voting rights in its decision-making process at all times considering the historical voting pattern at the shareholders’ meetings. 3 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company holds the majority of voting right based on an agreement with other investors. 4 The number of subsidiaries’ treasury stock is deducted from the total number of shares when calculating the controlling percentage ownership. Changes in scope of consolidation in 2017 are as follows: Changes Location Subsidiary Reason Included Korea KT Strategic Investment Fund No.4 Newly established KT Music Contents Investment Fund No.2 Newly established Excluded Korea KT Innoedu Co., Ltd. Shares disposed NgeneBio Percentage of ownership decreased Summarized information for consolidated subsidiaries as of and for the years ended December 31, 2015, 2016 and 2017, follows: (in millions of Korean won) 2015 Total assets Total Operating Profit (loss) For the year KT Powertel Co., Ltd. ￦ 113,515 ￦ 21,182 ￦ 104,527 ￦ (32,417 ) KT Linkus Co., Ltd. 77,141 65,745 116,095 3,449 KT Submarine Co., Ltd. 160,314 63,518 67,268 4,145 KT Telecop Co., Ltd. 269,191 134,966 302,844 (7,593 ) KT Hitel Co.,Ltd. 235,757 33,938 162,155 7,258 KT Service Bukbu Co., Ltd 2 31,879 22,627 89,498 (4,630 ) KT Service Nambu Co., Ltd 2 20,729 10,567 110,129 (5,055 ) BC Card Co., Ltd. 1 2,963,952 1,945,634 3,504,946 218,969 H&C Network 1 248,189 70,635 241,008 19,513 Nasmedia, Inc. 141,733 72,202 45,630 9,916 KTDS Co., Ltd. 1 162,518 116,654 423,015 12,836 KT M Hows Co., Ltd. 25,093 17,980 19,352 1,728 KT M&S Co., Ltd. 256,246 217,892 853,011 (18,776 ) GENIE Music Corporation(KT Music Corporation) 90,518 30,704 90,005 3,446 KT Skylife Co., Ltd. 1 711,294 217,850 668,521 72,987 KT Estate Inc. 1 1,603,438 260,292 254,776 27,487 KTSB Data service 23,063 1,730 4,390 (2,444 ) KT Innoedu Co., Ltd. 5,858 7,585 18,156 (4,288 ) KT Sat Co., Ltd. 679,959 210,110 133,326 27,174 KT Sports 15,341 11,643 51,801 (3,836 ) KT Music Contents Fund No.1 10,206 47 468 (111 ) KT-Michigan 5,401 — 861 (209 ) Autopion Co., Ltd. 7,102 3,317 10,585 1,123 KT M mobile 64,756 13,121 42,478 (36,725 ) KT Investment Co., Ltd 49,485 30,827 4,704 (219 ) NgeneBio 7,894 4,683 — (434 ) KTCS Corporation 1 346,949 194,367 1,066,556 13,685 KTIS Corporation 211,164 55,370 473,892 15,041 Korea Telecom Japan Co., Ltd. 13,889 14,393 25,652 (248 ) Korea Telecom China Co., Ltd. 909 198 1,748 (95 ) KT Dutch B.V. 1 29,402 27 161 118 Super iMax LLC 14,962 8,186 8,291 (2,220 ) East Telecom LLC 30,833 17,066 24,066 664 Korea Telecom America, Inc. 6,016 1,378 6,391 156 PT. KT Indonesia 22 — — (9 ) Olleh Rwanda Networks Ltd. 188,951 147,653 7,299 (28,721 ) KT Belgium 77,058 4 — (127 ) KT ORS Belgium 1,996 20 — (75 ) KBTO sp.zo.o. 1,471 1,817 — (328 ) Africa Olleh Services Ltd. 11,928 12,187 8,712 (923 ) (In millions of Korean won) 2016 Total assets Total liabilities Operating Profit (loss) For the year KT Powertel Co., Ltd. ￦ 113,725 ￦ 19,899 ￦ 81,390 ￦ 202 KT Linkus Co., Ltd. 64,318 56,953 117,587 (3,830 ) KT Submarine Co., Ltd. 156,993 55,573 84,137 5,146 KT Telecop Co., Ltd. 265,553 132,344 315,948 143 KT Hitel Co., Ltd. 249,202 46,941 198,994 4,298 KT Service Bukbu Co., Ltd. 32,863 24,580 182,952 694 KT Service Nambu Co., Ltd. 32,621 24,282 218,602 772 BC Card Co., Ltd. 1 3,651,065 2,602,404 3,567,512 163,131 H&C Network 1 272,110 80,983 266,613 14,749 Nasmedia, Inc. 1 263,925 159,502 70,037 11,972 KTDS Co., Ltd. 1 197,970 151,644 476,379 10,838 KT M Hows Co., Ltd. 28,539 18,466 19,922 2,865 KT M&S Co., Ltd. 247,854 227,507 724,144 (12,955 ) GENIE Music Corporation(KT Music Corporation) 110,080 41,953 111,450 8,235 KT Skylife Co., Ltd. 1 777,948 231,452 668,945 68,863 KT Estate Inc. 1 1,734,729 375,341 405,417 46,815 KTSB Data service 20,075 759 5,136 (1,983 ) KT Innoedu Co., Ltd. 6,477 7,259 15,599 103 KT Sat Co., Ltd. 744,653 253,041 144,594 36,266 KT Sports 16,925 13,573 48,476 (198 ) KT Music Contents Fund No.1 10,592 331 349 103 KT-Michigan 16,250 163 133 (514 ) Autopion Co., Ltd. 6,163 2,794 7,772 (409 ) KT M mobile 131,446 20,369 112,532 (40,041 ) KT Investment Co., Ltd. 1 39,506 23,123 10,130 (1,832 ) NgeneBio 6,361 4,733 244 (1,833 ) KTCS Corporation 1 322,768 166,642 955,050 7,892 KTIS Corporation 221,176 63,871 436,914 9,991 Korea Telecom Japan Co., Ltd. 3,592 5,374 5,122 (1,391 ) Korea Telecom China Co., Ltd. 532 188 930 60 KT Dutch B.V 34,197 73 166 85 Super iMax LLC 10,308 6,734 10,759 (1,802 ) East Telecom LLC 31,885 16,554 27,492 3,257 Korea Telecom America, Inc. 4,464 1,306 7,113 181 PT. KT Indonesia 16 — — (7 ) KT Rwanda Networks Ltd. 167,112 138,651 13,435 (31,455 ) KT Belguium 79,391 7 — (67 ) KT ORS Belgium 2,013 23 — (46 ) KBTO sp.zo.o. 1,166 2,378 21 (2,587 ) AOS Ltd. 10,025 3,179 14,481 (1,123 ) KT Hongkong Telecommunications Co., Ltd. 1,571 956 1,568 120 (In millions of Korean won) 2017 Total assets Total liabilities Operating Profit (loss) for the year KT Powertel Co., Ltd. 115,125 18,937 69,234 2,112 KT Linkus Co., Ltd. 59,344 51,516 112,043 725 KT Submarine Co., Ltd. 142,797 34,056 73,985 8,243 KT Telecop Co., Ltd. 264,353 131,633 317,591 2,885 KT Hitel Co., Ltd. 258,240 52,943 227,884 3,225 KT Service Bukbu Co., Ltd. 29,281 22,096 194,837 688 KT Service Nambu Co., Ltd. 36,076 26,412 232,996 875 BC Card Co., Ltd. 1 4,048,263 2,955,038 3,628,995 156,109 H&C Network 1 273,856 65,446 277,622 16,104 Nasmedia, Inc. 1 315,967 188,197 120,667 26,676 KTDS Co., Ltd. 1 144,922 93,343 459,266 11,584 KT M Hows Co., Ltd. 42,738 28,489 24,610 4,097 KT M&S Co., Ltd. 242,388 231,151 734,420 (9,707 ) GENIE Music Corporation(KT Music Corporation) 139,686 48,512 156,163 (3,401 ) KT Skylife Co., Ltd. 1 792,893 210,550 687,752 57,314 KT Estate Inc. 1 1,869,194 502,915 428,446 52,416 KTSB Data service 18,306 605 4,950 (1,651 ) KT Sat Co., Ltd. 742,391 220,804 147,649 29,601 KT Sports 11,131 7,805 53,357 (199 ) KT Music Contents Fund No.1 13,804 1,041 370 (499 ) KT Music Contents Fund No.2 7,500 11 — (11 ) KT-Michigan 14,575 147 159 (426 ) Autopion Co., Ltd. 6,306 3,530 6,679 (618 ) KT M mobile 93,601 21,453 159,684 (38,883 ) KT Investment Co., Ltd. 1 54,673 38,313 8,794 (619 ) KTCS Corporation 1 348,334 188,764 968,186 7,385 KTIS Corporation 223,818 62,569 438,597 8,337 Korea Telecom Japan Co., Ltd. 1 1,554 2,788 2,772 536 Korea Telecom China Co., Ltd. 665 32 1,030 348 KT Dutch B.V 30,312 50 206 169 Super iMax LLC 3,449 4,886 7,314 (4,584 ) East Telecom LLC 1 11,672 11,748 19,663 (9,118 ) Korea Telecom America, Inc. 3,694 791 6,783 109 PT. KT Indonesia 8 — — (6 ) KT Rwanda Networks Ltd. 2 151,359 139,561 15,931 (22,762 ) KT Belguium 86,455 8 49 (2 ) KT ORS Belgium 1,769 14 10 (10 ) KBTO sp.zo.o. 3,311 2,268 67 (3,456 ) AOS Ltd. 2 9,437 4,519 8,952 (682 ) KT Hongkong Telecommunications Co., Ltd. 2,578 1,497 7,304 494 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries included in liabilities.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Significant Accounting Policies	2. Significant Accounting Policies The following is a summary of significant accounting policies followed by the Group in the preparation of its financial statements. These policies have been consistently applied to all the years presented, unless otherwise stated. 2.1 Basis of Preparation The consolidated financial statements of the Group have been prepared in accordance with International Financial Reporting Standards(“IFRS”) as issued by the International Accounting Standards Board (“IASB”). The preparation of the consolidated financial statements requires the use of certain critical accounting estimates. It also requires management to exercise judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3. 2.2 Changes in Accounting Policy and Disclosures (1) New standards and amendments adopted by the Group The Group has applied the following standards and amendments for the first time for their annual reporting period commencing January 1, 2017. The adoption of these amendments did not have any material impact on the financial statements. - Statement of Cash Flows Amendments to IAS 7, Statement of Cash Flows non-cash - Income Tax Amendments to IAS 12 clarify how to account for deferred tax assets related to debt instruments measured at fair value. IAS 12 provides requirements on the recognition and measurement of current or deferred tax liabilities or assets. The amendments issued clarify the requirements on recognition of deferred tax assets for unrealized losses, to address diversity in practice - Disclosures of Interests in Other Entities Amendments to IFRS 12 clarify when an entity’s interest in a subsidiary, a joint venture or an associate is classified as held for sales in accordance with IFRS 5, the entity is required to disclose other information except for summarized financial information in accordance with IFRS 12. (2) New standards, amendments and interpretations not yet adopted Certain new accounting standards and interpretations that have been published that are not mandatory for annual reporting period commencing January 1, 2017 and have not been early adopted by the Group are set out below. - Amendments to IAS 28, Investments in Associates and Joint Ventures When an investment in an associate or a joint venture is held by, or it held indirectly through, an entity that is a venture capital organization, or a mutual fund, unit trust and similar entities including investment-linked insurance funds, the entity may elect to measure that investment at fair value through profit or loss in accordance with IFRS 9. The amendments clarify that an entity shall make this election separately for each associate of joint venture, at initial recognition of the associate or joint venture. The Group will apply these amendments retrospectively for annual periods beginning on or after January 1, 2018, and early adoption is permitted. The Group does not expect the amendments to have a significant impact on the financial statements. - Amendment to IAS 40, Transfers of Investment Property Paragraph 57 of IAS 40 clarifies that a transfer to, or from, investment property, including property under construction, can only be made if there has been a change in use that is supported by evidence, and provides a list of circumstances as examples. The amendment will be effective for annual periods beginning on or after January 1, 2018, with early adoption permitted. The Group does not expect the amendment to have a significant impact on the financial statements. - Amendments to IFRS 2, Share-based Payment Amendments to IFRS 2 clarify accounting for a modification to the terms and conditions of a share-based payment that changes the classification of the transaction from cash-settled to equity-settled. Amendments also clarify that the measurement approach should treat the terms and conditions of a cash-settled award in the same way as for an equity-settled award. The amendments will be effective for annual periods beginning on or after January 1, 2018, with early adoption permitted. The Group does not expect the amendments to have a significant impact on the financial statements. - Enactments to IFRIC 22, Foreign Currency Transaction and Advance Consideration According to these enactments, the date of the transaction for the purpose of determining the exchange rate to use on initial recognition of the related asset, expense or income (or part of it) is the date on which an entity initially recognizes the non-monetary non-monetary - Enactment of IFRS 16, Leases IFRS 16 Leases issued on May 22, 2017 is effective for annual periods beginning on or after January 1, 2019, with early adoption permitted. This standard will replace IAS 17 Leases, IFRIC 4 Determining whether an Arrangement contains a Lease, SIC-15 SIC-27 At inception of a contract, the entity shall assess whether the contract is, or contains, a lease. Also, at the date of initial application, the entity shall assess whether the contract is, or contains, a lease in accordance with the standard. However, the entity will not need to reassess all contracts with applying the practical expedient. As practical expedient, the entity can elect to apply the new guidance regarding the definition of a lease only to contracts entered into (or changed) on or after the date of initial application. Existing lease contracts will not need to be reassessed. This expedient must be consistently applied to all contracts. For a contract that is, or contains, a lease, the entity shall account for each lease component within the contract as a lease separately from non-lease right-of-use non-lease non-lease (1) Lessee accounting A lessee shall apply this standard to its leases either: • retrospectively to each prior reporting period presented applying IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors (Full retrospective application); or • retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial application. The Group has not yet elected the application method. The Group performed an impact assessment to identify potential financial effects of applying IFRS 16. The assessment was performed based on available information as at December 31, 2017 to identify effects on 2017 financial statements. The Group is analyzing the effects on the financial statements; however, it is difficult to provide reasonable estimates of financial effects until the analyses is complete. (2) Lessor accounting The Company expects the effect on the financial statements applying the new standard will not be significant - IFRS 9, Financial Instruments The new standard for financial instruments issued on September 25, 2015 are effective for annual periods beginning on or after January 1, 2018 with early application permitted. This standard will replace IAS 39, Financial Instruments: Recognition and Measurement The standard requires retrospective application with some exceptions. For example, an entity is not required to restate prior period in relation to classification and measurement (including impairment) of financial instruments. The standard requires prospective application of its hedge accounting requirements for all hedging relationships except the accounting for time value of options and other exceptions. IFRS 9, Financial Instruments An effective implementation of IFRS 9 requires preparation processes including financial impact assessment, accounting policy establishment, accounting system development and the system stabilization. The impact on the Group’s financial statements due to the application of the standard is dependent on judgements made in applying the standard, financial instruments held by the Group and macroeconomic variables. The Group performed an impact assessment to identify potential financial effects of applying IFRS 9. The assessment was performed based on available information as at December 31, 2017, and the results of the assessment are explained as below. (a) Classification and Measurement of Financial Assets When implementing IFRS 9, the classification of financial assets will be driven by the Group’s business model for managing the financial assets and contractual terms of cash flow. The following table shows the classification of financial assets measured subsequently at amortized cost, at fair value through other comprehensive income and at fair value through profit or loss. If a hybrid contract contains a host that is a financial asset, the classification of the hybrid contract shall be determined for the entire contract without separating the embedded derivative. Business model for the contractual cash flows characteristics Solely represent payments of principal and interest All other Hold the financial asset for the collection of the contractual cash flows Measured at amortized cost 1 Recognized at fair value through profit or loss 2 Hold the financial asset for the collection of the contractual cash flows and sale Recognized at fair value through other comprehensive income 1 Hold for sale Recognized at fair value through profit or loss 1 A designation at fair value through profit or loss is allowed only if such designation mitigates an accounting mismatch (irrevocable) 2 Equity investments not held for trading can be recorded in other comprehensive income (irrevocable). With the implementation of IFRS 9, the criteria to classify the financial assets at amortized cost or at fair value through other comprehensive income are more strictly applied than the criteria applied with IAS 39. Accordingly, the financial assets at fair value through profit or loss may increase by implementing IFRS 9 and may result an extended fluctuation in profit or loss. As of December 31, 2017, the Group owns loan and trade receivables of ￦ available-for-sales ￦ According to IFRS 9, a debt instrument is measured at amortized cost if: a) the objective of the business model is to hold the financial asset for the collection of the contractual cash flows, and b) the contractual cash flows under the instrument solely represent payments of principal and interest. Also, a debt instrument is measured at fair value through other comprehensive income if the objective of the business model is achieved both by collecting contractual cash flows and selling financial assets; and the contractual cash flows represents solely payments of principal and interest on a specific date under contract terms. Based on results from the impact assessment of IFRS 9, the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. According to IFRS 9, equity instruments that are not held for trading, the Group plans to elect an irrevocable election at initial recognition to classify the instruments as assets measured at fair value through other comprehensive income, which all subsequent changes in fair value being recognized in other comprehensive income and not recycled to profit or loss. As at December 31, 2017, the Group holds equity instruments of ￦ available-for-sale. According to IFRS 9, debt instruments those contractual cash flows do not represent solely payments of principal and interest and held for trading, and equity instruments that are not designated as instruments measured at fair value through other comprehensive income are measured at fair value through profit or loss. (b) Impairment: Financial Assets and Contract Assets The new impairment model requires the recognition of impairment provisions based on expected credit losses (ECL) rather than only incurred credit losses as is the case under IAS 39. It applies to financial assets classified at amortized cost, debt instruments measured at fair value through other comprehensive income, lease receivables, contract assets, loan commitments and certain financial guarantee contracts. As at December 31, 2017, the Group owns debt investment carried at amortized cost of ￦ ￦ held-to-maturity ￦ ￦ As a result of the impact assessment, the Group expects the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. (c) Hedge Accounting Hedge accounting mechanics (fair value hedges, cash flow hedges and hedge of net investments in a foreign operations) required by IAS 39 remains unchanged in IFRS 9, however, the new hedge accounting rules will align the accounting for hedging instruments more closely with the Group’s risk management practices. As a general rule, more hedge relationships might be eligible for hedge accounting, as the standard introduces a more principles-based approach. IFRS 9 allows more hedging instruments and hedged items to qualify for hedge accounting, and relaxes the hedge accounting requirement by removing two hedge effectiveness tests that are a prospective test to ensure that the hedging relationship is expected to be highly effective and a quantitative retrospective test (within range of 80-125 ￦ ￦ The Group has performed an impact assessment with an assumption that the Group applies hedge accounting in accordance with IFRS 9. As a result of the impact assessment, the Group expects the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. - IFRS 15 Revenue from Contracts with Customers The Group will apply IFRS 15 Revenue from Contracts with Customers Revenue Construction Contracts, SIC-31 , Revenue-Barter Transactions Involving Advertising Services IFRIC 13 Customer Loyalty Programs, IFRIC 15 Agreements for the Construction of Real Estate and IFRIC 18 Transfers of assets from customers Revenue from Contracts with Customers IAS 18 and other current revenue standard identify revenue as income that arises in the course of ordinary activities of an entity and provides guidance on a variety of different types of revenue, such as, sale of goods, rendering of services, interest, dividends, royalties and construction contracts. However, the new standard is based on the principle that revenue is recognized when control of a good or service transfers to a customer so the notion of control replaces the existing notion of risks and rewards. A new five-step process must be applied before revenue from contract with customers can be recognized: • Identify contracts with customers • Identify the separate performance obligation • Determine the transaction price of the contract • Allocate the transaction price to each of the separate performance obligations, and • Recognize the revenue as each performance obligation is satisfied. The Group formed a task force team since fourth quarter of 2014 for preparation of implementing IFRS 15 Revenue from Contracts with Customers. Also the Group develops the internal control system and implements accounting process system by analyzing the Group’s revenue structure with accounting experts and IT specialists. IFRS 15 will affect not only accounting treatments but also the general business practice including sales strategy and operational structures. Therefore, the Group accomplished an orientation program for both Group’s directors and employees, and periodically reported to the managements about implementation plan and progress. Group identified the following areas are likely to be affected in general. (a) Identifying performance obligations The Group provides telecommunication services and sells handsets as their main business. With the implementation of IFRS 15, the Group identifies performance obligations with a customer such as providing telecommunication services, selling handsets and other. The timing of revenue recognition depends on a performance obligation is satisfied at a point in time or over time. Where a performance obligation is satisfied over time, the related revenue is also recognized over time. (b) Allocation the transaction price and Revenue recognition With implementation of IFRS 15, the Group allocated the transaction price to each performance obligation identified in a contract based on the relative stand-alone selling prices of the goods or services being provided to the customer. To allocate the transaction price to each performance obligation on a relative stand-alone price basis, the Group determines the stand-alone selling price at contract inception of the distinct good or service underlying each performance obligation in the contract and allocate the transaction price in proportion to those stand-alone selling price. The stand-alone selling price is the price at which the Group would sell a promised good or service separately to the customer. The best evidence of a stand-alone selling price is the observable price of a good or service when the Group sells that good or service separately in similar circumstances and to similar customers. The Group recognizes the allocated amount as contract assets or contract liabilities, and amortizes it through the remaining period which is adjusted in operating income. (c) Incremental costs of obtaining a contract The Group pays the commission fees when new customer subscribe for telecommunication services. The incremental contract acquisition costs are those commission fees that the Group incurs to acquire a contract with a customer that it would not have incurred if the contract had not been acquired. According to IFRS 15, the Group recognizes as an asset the incremental contract acquisition costs and amortize it over the expected period of benefit. However, as a practical expedient, the Group may recognize the incremental contract acquisition costs as an expense when incurred if the amortization period of the asset is one year or less. With implementation of IFRS 15, the Group’s operating income and expenses are expected to be decreased. Under the modified retrospective method, we will apply the rules to all open contracts existing as of January 1, 2018, recognizing in beginning retained earnings for 2018 an adjustment between ￦ ￦ 2.3 Consolidation The Group has prepared the consolidated financial statements in accordance with IFRS 10 Consolidated Financial Statements (1) Subsidiaries Subsidiaries are all entities over which the Group has control. The Group controls an entity when the Group is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power to direct the activities of the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Group. They are deconsolidated from the date that control ceases. The acquisition method of accounting is used to account for business combinations by the Group. The consideration transferred is measured at the fair values of the assets transferred, and identifiable assets acquired and liabilities and contingent liabilities assumed in a business combination are measured initially at their fair values at the acquisition date. The Group recognizes any non-controlling acquisition-by-acquisition non-controlling non-controlling The excess of consideration transferred, amount of any non-controlling Intercompany transactions, balances and unrealized gains on transactions between group companies are eliminated. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment of the transferred asset. Accounting policies of subsidiaries have been changed where necessary to ensure consistency with the policies adopted by the Group. (2) Changes in ownership interests in subsidiaries without change of control Any difference between the amount of the adjustment to non-controlling (3) Disposal of subsidiaries When the Group ceases to consolidate for a subsidiary because of a loss of control, any retained interest in the subsidiary is remeasured to its fair value with the change in carrying amount recognized in profit or loss. (4) Associates Associates are all entities over which the Group has significant influence, and investments in associates are initially recognized at acquisition cost using the equity method. Unrealized gains on transactions between the Group and its associates are eliminated to the extent of the Group’s interest in the associates. If there is any objective evidence that the investment in the associate is impaired, the Group recognizes the difference between the recoverable amount of the associate and its book amount as impairment loss. (5) Joint arrangement A joint arrangement, wherein two or more parties have joint control, is classified as either a joint operation or a joint venture. A joint operator recognizes its direct right to the assets, liabilities, revenues and expenses of joint operations and its share of any jointly held or incurred assets, liabilities, revenues and expenses. A joint venturer has rights to the net assets relating to the joint venture and accounts for that investment using the equity method. 2.4 Segment Reporting Information of each operating segment is reported in a manner consistent with the business segment reporting provided to the chief operating decision-maker (Note 33). The chief operating decision-maker is responsible for allocating resources and assessing performance of the operating segments. 2.5 Foreign Currency Translation (1) Functional and presentation currency Items included in the financial statements of each of the Group’s entities are measured using the currency of the primary economic environment in which the each entity operates (the “functional currency’). The consolidated financial statements are presented in Korean won, which is the Controlling Company’s functional and presentation currency. (2) Transactions and balances Foreign currency transactions are translated into the functional currency using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at year end exchange rates are generally recognized in profit or loss. Non-monetary non-monetary non-monetary available-for-sale (3) Translation to the presentation currency The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each statement of financial position presented are translated at the closing rate at the end of the reporting period, • income and expenses for each statement of profit or loss are translated at average exchange rates for the period, • equity is translated at the historical exchange rate, and • all resulting exchange differences are recognized in other comprehensive income. 2.6 Cash and Cash Equivalents Cash and cash equivalents include cash on hand, deposits held at call with banks, and other short-term highly liquid investments with original maturities of less than three months. 2.7 Financial Assets (1) Classification and measurement The Group classifies its financial assets into the following categories: financial assets at fair value through profit or loss, available-for-sale held-to-maturity The Group may designate the entire hybrid (combined) contract as a financial asset at fair value through profit or loss for a contract that contains one or more embedded derivatives. At initial recognition, the Group measures a financial asset at its fair value plus, in the case of a financial asset not at fair value through profit or loss, transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at fair value through profit or loss are expensed in profit or loss. Available-for-sale held-to-maturity Gains or losses arising from changes in the fair value of financial assets at fair value through profit or loss are recognized in profit or loss within other income or other expenses. Gains or losses arising from changes in the available-for-sale (2) Impairment The Group assesses at the end of each reporting period whether there is objective evidence that a financial asset or a group of financial assets is impaired. A financial asset or a group of financial assets is impaired and impairment losses are incurred only if there is objective evidence of impairment as a result of one or more events that occurred after the initial recognition of the asset (a ‘loss event’) and that loss event (or events) has an impact on the estimated future cash flows of the financial asset or a group of financial assets that can be reliably estimated. Impairment of loans and receivables is presented as a deduction in an allowance account. Impairment of other financial assets is directly deducted from their carrying amount. The Group writes off financial assets when the assets are determined to be no longer recoverable. The criteria that the Group uses to determine that there is objective evidence of an impairment loss include: • Significant financial difficulty of the issuer or obligor; • A breach of contract, such as a default or delinquency in interest or principal payments; • For economic or legal reasons relating to the borrower’s financial difficulty, granting to the borrower a concession that the lender would not otherwise consider; • It becomes probable that the borrower will enter bankruptcy or other financial reorganization; • The disappearance of an active market for that financial asset because of financial difficulties; or • Observable data indicating that there is a measurable decrease in the estimated future cash flows from a portfolio of financial assets since the initial recognition of those assets, although the decrease cannot yet be identified with the individual financial assets in the portfolio. (3) Derecognition If the Group transfers a financial asset and the transfer does not result in derecognition because the Group has retained substantially of all risks and rewards of ownership of the transferred asset due to a recourse in the event the debtor defaults, the Group continues to recognize the transferred asset in its entirety and recognizes a financial liability for the consideration received. The related financial liability is classified as ‘borrowings’ in the statement of financial position. (4) Offsetting of financial instruments Financial assets and liabilities are offset and the net amount reported in the statements of financial position where there is a legally enforceable right to offset the recognized amounts and there is an intention to settle on a net basis or realize the assets and settle the liability simultaneously. The legally enforceable right must not be contingent on future events and must be enforceable in the normal course of business and in the event of default, insolvency or bankruptcy of the Group or the counterparty. 2.8 Derivative Instruments Derivatives are initially recognized at fair value on the date when a derivative contract is entered into and are subsequently remeasured at their fair value. Changes in the fair value of the derivatives that are not qualified for hedge accounting are recognized in the statement of profit or loss within ‘other income (expenses)’ and ‘finance income (expenses)’ according to the nature of transactions. If the Group uses a valuation technique that incorporates data not obtained from observable markets for the fair value at initial recognition of the financial instrument, there may be a difference between the transaction price and the amount determined using that valuation technique (Day 1 profit and loss). In these circumstances, the fair value of the financial instrument is recognized as the transaction price and the difference is amortized by using the straight-line method over the life of the financial instrument. If the fair value of the financial instrument is subsequently determined using observable market inputs, the remaining deferred amount is recognized in profit or loss in the statement of profit or loss. The Group applies cash flow hedge accounting to hedge the risks of foreign exchange and interest rates of the variable rate foreign currency bonds. The effective portion of changes in the fair value of derivatives that are designated and qualify as cash flow hedges is recognized in other comprehensive income. The gain or loss relating to the ineffective portion is recognized immediately as finance income (expenses) in the statement of profit or loss. Amounts of changes in fair value of effective hedging instruments accumulated in other comprehensive income are recognized as ‘finance income (expenses)’ for the periods when the corresponding transactions affect profit or loss. When a forecast transaction is no longer expected to occur, the cumulative gain or loss that is reported in other comprehensive income is recognized as ‘finance income (expenses)’. If the hedge no longer meets the criteria for hedge accounting, the adjustment to the carrying amount of a hedged item for which the effective interest method is used is amortized to profit or loss over the period to maturity. 2.9 Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined using the moving average method, except for inventories in-transit 2.10 Non-current Held-for-sale Non-current held-for-sale 2.11 Property and Equipment Property and equipment are stated at its cost less accumulated depreciation and accumulated impairment losses. Historical cost includes expenditures that is directly attributable to the acquisition of the items. Depreciation of all property, plant, and equipment, except for land is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives, as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) Others 2 – 40 years Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years The depreciation method, residual values and useful lives of property and equipment are reviewed at the end of each reporting period and, if appropriate, accounted for as changes in accounting estimates. 2.12 Investment Property Investment property is a property held to earn rentals or for capital appreciation. An investment property is measured initially at its cost. After recognition as an asset, investment property is carried at cost less accumulated depreciation and impairment losses. Investment property, except for land, is depreciated using the straight-line method over their useful lives from 10 to 40 years. 2.13 Intangible Assets (1) Goodwill Goodwill is measured as explained in Note 2.3 (1) and goodwill arising from acquisition of subsidiaries and business are included in intangible assets. Goodwill is tested annually for impairment and carried at cost less accumulated impairment losses. (2) Intangible assets except goodwill Intangible assets, except for goodwill, are initially recognized at its historical cost, and carried at cost less accumulated amortization and accumulated impairment losses. Membership rights (condominium membership and golf membership) and broadcast rights that have an indefinite useful life are not subject to amortization because there is no foreseeable limit to the period over which the assets are expected to be utilized. The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 6 years Frequency usage rights 5 –10 years Others 1 2 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life. 2.14 Borrowing Costs General and specific borrowing costs that are directly attributable to the acquisition, construction or production of a qualifying asset are capitalized during the period of time that is required to complete and prepare the asset for its intended use or sale. Investment income earned on the temporary investment of specific borrowings pending their expenditure on qualifying assets is deducted from the borrowing costs eligible for capitalization. Other borrowing costs are expensed in the period in which they are incurred. 2.15 Government Grants Grants from the government are recognized at their fair value where there is a reasonable assurance that the grant will be received and the Group will comply wit

Critical Accounting Estimates a

Critical Accounting Estimates and Assumptions	12 Months Ended
	Dec. 31, 2017
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Critical Accounting Estimates and Assumptions	3. Critical Accounting Estimates and Assumptions The Group makes estimates and assumptions concerning the future. The estimates and assumptions are continuously evaluated with consideration to factors such as events reasonably predictable in the foreseeable future within the present circumstance according to historical experience. The resulting accounting estimates will, by definition, seldom equal the related actual results. The estimates and assumptions that have a significant risk of causing a material adjustment to the carrying amounts of assets and liabilities within the next financial year are addressed below. 3.1 Impairment of Goodwill The Group tests whether goodwill has suffered any impairment on an annual basis. The recoverable amount of cash-generating units (CGUs) is determined based on value-in-use 3.2 Income Taxes The Group is operating in numerous countries and the income generated from these operations is subject to income taxes based on tax laws and interpretations of tax authorities in numerous jurisdictions. There are many transactions and calculations for which the ultimate tax determination is uncertain (Note 28). If certain portion of the taxable income is not used for investments or increase in wages or dividends in accordance with the Tax System For Recirculation of Corporate Income 3.3 Fair Value of Derivatives and Financial Instruments The fair value of financial instruments that are not traded in an active market is determined by using valuation techniques. The Group uses its judgment to select a variety of methods and make assumptions that are mainly based on market conditions existing at the end of each reporting period (Note 36). 3.4 Provision for Impairment The Group recognizes provisions for accounting of estimated loss in customers’ insolvency. When the provision for impairment is estimated, it is based on the aging analysis of trade receivables balances, incurred loss experience, customers’ credit rates and changes of payment terms. If the customer’s financial position becomes worse, the actual loss amount will be increased more than the estimated. 3.5 Net defined benefit liability The present value of net defined benefit liability depends on a number of factors that are determined on an actuarial basis using a number of assumptions including the discount rate (Note 17). 3.6 Deferred Revenue Service installation fees and initial subscription fees related to activation of service are deferred and recognized as revenue over the expected periods of customer relationships. The estimate of the expected terms of customer relationship is based on the historical data. If management’s estimate changes, it may cause significant differences in the timing of revenue recognition and amounts recognized. 3.7 Provisions As described in Note 16, the Group records provisions for litigation and assets retirement obligations at the end of the reporting period. The provisions are estimated based on the factors such as the historical experiences. 3.8 Useful Lives of Property and Equipment and Investment Property The property and equipment, intangible assets, and investment properties, excluding land, goodwill, condominium memberships and golf club memberships, are depreciated using the straight-line method over their useful lives. The estimated useful lives are determined based on expected usage of the assets and the estimates can be materially affected by technical changes and other factors. The Group will increase depreciation expenses if the useful lives are considered shorter than the previously estimated useful lives.

Financial Instruments by Catego

Financial Instruments by Category	12 Months Ended
	Dec. 31, 2017
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Financial Instruments by Category	4. Financial Instruments by Category Financial instruments by category as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Financial assets Loans and receivables Assets at fair and loss Derivatives Available- for-sale Held-to- Maturity Total Cash and cash equivalents ￦ 2,900,311 ￦ — ￦ — ￦ — ￦ — ￦ 2,900,311 Trade and other receivables 6,036,363 — — — — 6,036,363 Other financial assets 716,769 6,277 227,318 404,774 30,143 1,385,281 (In millions of Korean won) 2016 Financial liabilities Liabilities at Derivatives used for Financial Total Trade and other payables ￦ — ￦ — ￦ 8,328,082 ￦ 8,328,082 Borrowings — — 8,120,791 8,120,791 Other financial liabilities 1,973 14,928 91,763 108,664 (In millions of Korean won) 2017 Financial assets Loans and receivables Assets at fair and loss Derivatives Available- for-sale Held-to- Maturity Total Cash and cash equivalents ￦ 1,928,182 ￦ — ￦ — ￦ — ￦ — ￦ 1,928,182 Trade and other receivables 6,643,115 — — — — 6,643,115 Other financial assets 1,333,317 5,813 7,389 380,953 151 1,727,623 (In millions of Korean won) 2017 Financial liabilities Liabilities at Derivatives used for Financial Total Trade and other payables ￦ — ￦ — ￦ 8,425,503 ￦ 8,425,503 Borrowings — — 6,683,662 6,683,662 Other financial liabilities 5,051 93,770 87,669 186,490 Gains or losses arising from financial instruments by category for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Loans and receivables Interest income 1, 4 ￦ 85,603 ￦ 129,813 ￦ 108,608 Loss on foreign currency transaction (365 ) (7,493 ) (11,949 ) Gain(loss) on foreign currency translation 1,921 3,083 (12,354 ) Loss on disposal (2,539 ) (15,838 ) (20,351 ) Loss on valuation (141,555 ) (92,589 ) (44,219 ) Assets at fair value through profit or loss Dividend income — — 1 Gain on disposal 368 186 153 Loss on valuation — (7,184 ) (464 ) Derivatives used for hedging Loss on transaction (5,157 ) — (58,569 ) Gain(loss) on valuation 141,512 109,436 (63,640 ) Other comprehensive income for the year 2 100,401 60,501 (44,429 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (88,003 ) (71,915 ) 50,231 Available-for-sale Interest income 1,4 73 40 453 Dividend income 7,733 3,926 5,174 Gain on disposal 131,045 22,695 89,598 Impairment loss (1,471 ) (966 ) (6,137 ) Other comprehensive income for the year 2 47,381 10,925 51,235 Reclassified to profit or loss from other comprehensive income for the year 2 (83,397 ) (3,840 ) (55,450 ) Held-to-Maturity Interest income 1,4 226 213 — Liabilities at fair value through profit and loss Gain(loss) on disposal (850 ) (632 ) — Gain(loss) on valuation (2,006 ) 33 (3,078 ) Derivatives used for hedging Gain(loss) on transactions (273 ) 8,329 — Loss on valuation (1,733 ) (138 ) (145,885 ) Other comprehensive income for the year 2 11,513 4,295 (66,624 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (9,959 ) (3,956 ) 91,698 Financial liabilities at amortized cost Interest expense 4 (385,925 ) (337,219 ) (302,464 ) Gain(loss) foreign currency transaction (23,416 ) (7,518 ) 62,347 Gain(loss) foreign currency translation (166,254 ) (112,864 ) 225,695 Total ￦ (385,127 ) ￦ (308,677 ) ￦ (150,420 ) 1 BC Card, a subsidiary of the Group, recognized interest income as operating revenue. Interest income recognized as operating revenue is ￦ ￦ ￦ 2 The amounts directly reflected in equity after adjustments of deferred income tax. 3 During the year, certain derivatives of the Group were settled and the related gain or loss on valuation of cash flow hedge in other comprehensive income was reclassified to profit or loss for the year. 4 BC Card recognized gain/loss on foreign currency transaction as operating income and expenses. During the year, related gain/loss on foreign currency transaction recognized as operating income and expense is ￦ ￦

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2017
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Cash and Cash Equivalents	5. Cash and Cash Equivalents Restricted cash and cash equivalents as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) Type 2016 2017 Description Restricted cash and cash equivalents Restricted deposit ￦ ￦ Deposit restricted for governmental project and others Cash and cash equivalents in the statement of financial position equal to cash and cash equivalents in the statement of cash flows.

Trade and Other Receivables

Trade and Other Receivables	12 Months Ended
	Dec. 31, 2017
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Trade and Other Receivables	6. Trade and Other Receivables Trade and other receivables as of December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Total Allowance doubtful Present value Carrying amount Current assets Trade receivables ￦ 3,161,234 ￦ (470,239 ) ￦ (5,343 ) ￦ 2,685,652 Other receivables 2,763,942 (121,972 ) (270 ) 2,641,700 ￦ 5,925,176 ￦ (592,211 ) ￦ (5,613 ) ￦ 5,327,352 Non-current assets Trade receivables ￦ 263,367 ￦ (632 ) ￦ (12,835 ) ￦ 249,900 Other receivables 507,251 (19,644 ) (28,496 ) 459,111 770,618 (20,276 ) (41,331 ) 709,011 2017 (In millions of Korean won) Total Allowance doubtful Present value Carrying amount Current assets Trade receivables ￦ 3,286,169 ￦ (438,817 ) ￦ (7,508 ) ￦ 2,839,844 Other receivables 3,041,028 (66,402 ) (187 ) 2,974,439 ￦ 6,327,197 ￦ (505,219 ) ￦ (7,695 ) ￦ 5,814,283 Non-current assets Trade receivables ￦ 366,107 ￦ (610 ) ￦ (12,803 ) ￦ 352,694 Other receivables 522,459 (17,970 ) (28,351 ) 476,138 ￦ 888,566 ￦ (18,580 ) ￦ (41,154 ) ￦ 828,832 Details of changes in allowance for doubtful accounts the years ended December 31, 2016 and 2017, are as follows: 2015 2016 2017 (In millions of Korean won) Trade Other Trade Other Trade Other Beginning balance ￦ 527,617 ￦ 311,082 ￦ 468,741 ￦ 250,842 ￦ 470,871 ￦ 141,616 Provision 95,489 46,066 84,975 7,736 38,888 5,809 Reversal or written-off (135,318 ) (33,282 ) (80,518 ) (108,638 ) (70,121 ) (61,220 ) Changes in the scope of consolidation (16,752 ) (69,732 ) 215 56 (107 ) (35 ) Others (2,232 ) (3,272 ) (2,542 ) (8,380 ) (104 ) (1,798 ) Ending balance ￦ 468,741 ￦ 250,842 ￦ 470,871 ￦ 141,616 ￦ 439,427 ￦ 84,372 Provisions for impairment on trade and other receivables are recognized as operating expenses, other expenses and finance costs. Details of aging analysis of trade receivables as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Neither past due nor impaired ￦ 2,377,637 ￦ 2,661,406 Past due and impaired Up to 6 months 685,288 701,032 6 months to 12 months 87,547 70,190 Over 12 months 255,951 199,337 1,028,786 970,559 Less: Allowance for doubtful accounts (470,871 ) (439,427 ) ￦ 2,935,552 ￦ 3,192,538 Details of other receivables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Loans ￦ 80,308 ￦ 84,682 Receivables 1 2,709,177 2,970,346 Accrued income 9,903 12,186 Refundable deposits 390,035 391,458 Loans receivable 10,355 34,273 Finance lease receivables 16,280 20,526 Others 26,369 21,478 Less: Allowance for doubtful accounts (141,616 ) (84,372 ) ￦ 3,100,811 ￦ 3,450,577 1 The settlement receivables of BC Card Co., Ltd. of ￦ ￦ Details of aging analysis of other receivables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Neither past due nor impaired ￦ 2,971,239 ￦ 3,271,949 Past due and impaired Up to 6 months 134,231 169,894 6 months to 12 months 12,805 16,052 Over 12 months 124,152 77,054 271,188 263,000 Less: Allowance for doubtful accounts (141,616 ) (84,372 ) Total ￦ 3,100,811 ￦ 3,450,577 The maximum exposure of trade and other receivables to credit risk is the carrying amount of each class of receivables mentioned above as of December 31, 2017.

Other Financial Assets and Liab

Other Financial Assets and Liabilities	12 Months Ended
	Dec. 31, 2017
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Other Financial Assets and Liabilities	7. Other Financial Assets and Liabilities Details of other financial assets and liabilities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other financial assets Financial assets at fair value through profit or loss ￦ 6,277 ￦ 5,813 Derivatives used for hedge 227,318 7,389 Financial instruments 1 716,769 1,333,317 Available-for-sale financial assets 1 404,774 380,953 Held-to-maturity investments 30,143 151 Less: Non-current (664,726 ) (754,992 ) Current ￦ 720,555 ) ￦ 972,631 ) Other financial liabilities Financial liabilities at fair value through the profit or loss ￦ 1,973 ￦ 5,051 Derivatives used for hedge 14,928 93,770 Other financial liabilities 91,763 87,669 Less: Non-current (108,431 ) (149,267 ) Current ￦ 233 ￦ 37,223 1 As of December 31, 2017, MMW(Money Market Wrap) and MMT(Money Market Trust) amounting to ￦ ￦ ￦ Financial instruments at fair value through profit or loss as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Assets Liabilities Assets Liabilities Financial instruments at fair value through profit and loss ￦ 6,277 ￦ — ￦ 5,813 ￦ — Other derivatives liabilities ￦ — ￦ 1,973 ￦ — ￦ 5,051 The valuation gains and losses on financial assets and liabilities at fair value through profit or loss and held for trading for the years ended December 31, 2015, 2016 and 2017, are as follows: Financial instruments at fair value through profit or loss 2015 2016 2017 (in millions of Korean won) Valuation Valuation Valuation Valuation Valuation Valuation Valuation gains and losses on financial assets ￦ — ￦ — ￦ 470 ￦ 7,654 ￦ — ￦ 464 Total ￦ — ￦ — ￦ 470 ￦ 7,654 ￦ — ￦ 464 Held for trading 2015 2016 2017 (in millions of Korean won) Valuation Valuation Valuation Valuation Valuation Valuation Valuation gains and losses on financial assets ￦ — ￦ 2,006 ￦ 33 ￦ — ￦ — ￦ 3,078 Total ￦ — ￦ 2,006 ￦ 33 ￦ — ￦ — ￦ 3,078 The maximum exposure of debt securities of financial instruments at fair value through profit or loss to credit risk is carrying amount as of December 31, 2017. Derivatives used for hedge as of December 31, 2016 and 2017, are as follows: 2016 2017 (in millions of Korean won) Assets Liabilities Assets Liabilities Interest rate swap 1 ￦ — ￦ 3,278 ￦ — ￦ 2,633 Currency swap 2 214,648 11,650 7,389 81,300 Currency forwards 3 12,670 — — 9,837 Total 227,318 14,928 7,389 93,770 Less: non-current (97,220 ) (14,695 ) (4,675 ) (56,547 ) Current ￦ 130,098 ￦ 233 ￦ 2,714 ￦ 37,223 1 The interest rate swap contract is to hedge the risk of variability in future fair value of the bond. 2 The currency swap contract is to hedge the risk of variability in cash flow from the bond. In applying the cash flow hedge accounting, the Group hedges its exposures to cash flow fluctuation until September 7, 2034. 3 The currency forward contract is to hedge the risk of variability in cash flow from transactions in foreign currencies due to changes in foreign exchange rate. The full value of a hedging derivative is classified as a non-current asset or liability if the remaining maturity of the hedged item is more than 12 months and, as a current asset or liability, if the maturity of the hedged item is less than 12 months. The valuation gains and losses on the derivatives contracts for the years ended December 31, 2015, 2016 and 2017, are as follows: (in millions of 2015 2016 2017 Type of Valuation Valuation Other comprehensive 1 Valuation Valuation Other comprehensive 1 Valuation Valuation Other comprehensive 1 Interest rate swap ￦ — ￦ — ￦ (2,858 ) ￦ — ￦ 148 ￦ (142 ) ￦ 38 ￦ — ￦ 637 Currency swap 141,512 1,733 150,255 97,158 (10 ) 85,479 19 187,468 (146,752 ) Currency forwards — — 247 12,278 — 146 — 22,114 (393 ) Total ￦ 141,512 ￦ 1,733 ￦ 147,644 ￦ 109,436 ￦ 138 ￦ 85,483 ￦ 57 ￦ 209,582 ￦ (146,508 ) 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling interest. The ineffective portion recognized in profit or loss on the cash flow hedge is valuation gain of ￦ ￦ ￦ Details of available-for-sale financial assets as of December 31, 2016, and 2017 are as follows: (In millions of Korean won) 2016 2017 Marketable equity securities ￦ 5,387 ￦ 6,859 Non-marketable equity securities 372,703 364,195 Debt securities 26,684 9,899 Total 404,774 380,953 Less: non-current (384,798 ) (379,488 ) Current ￦ 19,976 ￦ 1,465 Changes of available-for-sale financial assets for the years ended December 31, 2016, and 2017 are as follows: (In millions of Korean won) 2016 2017 Beginning ￦ 360,037 ￦ 404,774 Acquisition 44,302 89,027 Disposal (18,161 ) (129,682 ) Valuation 1 14,413 67,593 Impairment (966 ) (6,137 ) Reclassification 5,149 (44,622 ) Changes in scope of consolidation — — Ending ￦ 404,774 ￦ 380,953 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling interest. The maximum exposure of debt securities of available-for-sale financial assets to credit risk is carrying amount as of December 31, 2017. Available-for-sale financial assets are measured at fair value. However, non-marketable equity securities that do not have quoted market prices in an active market and the fair value of which cannot be reliably measured are recognized at cost and the impairment loss is recognized if any. Investment in Korea Software Financial Cooperative amounting to ￦

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
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Inventories	8. Inventories Inventories as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Acquisition Valuation Book Acquisition Valuation Book Merchandise ￦ 403,938 ￦ (46,634 ) ￦ 357,304 ￦ 504,321 ￦ (58,293 ) ￦ 446,028 Others 97,778 (494 ) 97,284 195,999 — 195,999 Total ￦ 501,716 ￦ (47,128 ) ￦ 454,588 ￦ 700,320 ￦ (58,293 ) ￦ 642,027 Cost of inventories recognized as expenses for year ended December 31, 2017, amounts to ￦ ￦ ￦ ￦ ￦ ￦

Other Assets and Liabilities

Other Assets and Liabilities	12 Months Ended
	Dec. 31, 2017
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Other Assets and Liabilities	9. Other Assets and Liabilities Other assets and liabilities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other assets Advance payments ￦ 148,299 ￦ 164,950 Prepaid expenses 255,464 241,078 Others 13,471 5,998 Less: Non-current (106,099 ) (107,166 ) Current ￦ 311,135 ￦ 304,860 Other liabilities Advances received ￦ 281,071 ￦ 375,792 Withholdings 89,679 85,142 Unearned revenue 24,142 23,036 Others 6,160 11,629 Less: Non-current (58,761 ) (237,284 ) Current ￦ 342,291 ￦ 258,315

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2017
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Property, Plant and Equipment	10. Property, Plant and Equipment Changes in property, plant and equipment for the years ended December 31, 2016 and 2017, are as follows: 2016 (in millions of Korean won) Land Buildings Machinery Others Construction- Total Acquisition cost ￦ 1,287,749 ￦ 3,558,460 ￦ 34,388,584 ￦ 1,951,749 ￦ 1,033,777 ￦ 42,220,319 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,459,416 ) (24,879,791 ) (1,400,766 ) (1,300 ) (27,741,405 ) Beginning, net 1,287,617 2,099,044 9,508,793 550,983 1,032,477 14,478,914 Acquisition 291 3,608 247,431 146,471 2,297,346 2,695,147 Disposal/Abandonment (855 ) (1,650 ) (112,135 ) (8,155 ) (3,357 ) (126,152 ) Depreciation — (135,389 ) (2,498,837 ) (143,978 ) — (2,778,204 ) Impairment — — 361 (47,086 ) — (46,725 ) Transfer in (out) 4,274 136,041 2,060,936 11,073 (2,212,324 ) — Inclusion in scope of consolidation — — 68 764 — 832 Others 17,625 23,078 53,568 14,851 (20,823 ) 88,299 Ending, net ￦ 1,308,952 ￦ 2,124,732 ￦ 9,260,185 ￦ 524,923 ￦ 1,093,319 ￦ 14,312,111 Acquisition cost ￦ 1,309,084 ￦ 3,729,228 ￦ 35,106,184 ￦ 1,895,332 ￦ 1,093,941 ￦ 43,133,769 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,604,496 ) (25,845,999 ) (1,370,409 ) (622 ) (28,821,658 ) 2017 (In millions of Korean won) Land Buildings Machinery Others Construction- Total Acquisition cost ￦ 1,309,084 ￦ 3,729,228 ￦ 35,106,184 ￦ 1,895,332 ￦ 1,093,941 ￦ 43,133,769 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,604,496 ) (25,845,999 ) (1,370,409 ) (622 ) (28,821,658 ) Beginning, net 1,308,952 2,124,732 9,260,185 524,923 1,093,319 14,312,111 Acquisition 1,948 120 237,218 129,464 2,262,681 2,631,431 Disposal and termination (4,656 ) (4,022 ) (176,085 ) (8,242 ) (3,133 ) (196,138 ) Depreciation — (135,242 ) (2,469,459 ) (150,535 ) — (2,755,236 ) Impairment (Recovery of impairment) — — (9,256 ) (1 ) (28 ) (9,285 ) Transfer in (out) 26,764 25,305 2,227,808 10,344 (2,600,908 ) (310,687 ) Exclusion from scope of consolidation — (19 ) (772 ) (120 ) (34 ) (945 ) Transfer from(to) investment properties (64,449 ) 1,793 — 1,184 — (61,472 ) Others 98 (245 ) (8,830 ) (179 ) (38,304 ) (47,460 ) Ending, net ￦ 1,268,657 ￦ 2,012,422 ￦ 9,060,809 ￦ 506,838 ￦ 713,593 ￦ 13,562,319 Acquisition cost ￦ 1,268,789 ￦ 3,750,861 ￦ 35,971,877 ￦ 1,920,571 ￦ 714,706 ￦ 43,626,804 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,738,439 ) (26,911,068 ) (1,413,733 ) (1,113 ) (30,064,485 ) Details of property, plant and equipment provided as collateral as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Carrying Secured Related line item Related Secured party Land and Buildings ￦ 13,337 ￦ 16,009 Borrowings ￦ 11,540 Standard Korea Others 55,951 43,506 25,379 Shinhan Bank (In millions of Korean won) 2017 Carrying Secured Related line item Related Secured party Land and Buildings 13,115 15,995 Borrowings 2,730 Standard Korea Others 53,757 38,570 16,071 Shinhan Bank The borrowing costs capitalized for qualifying assets amount to ￦ ￦

Investment Properties

Investment Properties	12 Months Ended
	Dec. 31, 2017
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Investment Properties	11. Investment Properties Changes in investment properties for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Land Buildings Construction-in- Total Acquisition cost ￦ 340,790 ￦ 1,011,236 ￦ 74,208 ￦ 1,426,234 Less: Accumulated depreciation — (324,164 ) — (324,164 ) Beginning 340,790 687,072 74,208 1,102,070 Acquisition 51 417 160,138 160,606 Disposal/Abandonment (5,837 ) (1,802 ) — (7,639 ) Depreciation — (43,575 ) — (43,575 ) Transfer (32,254 ) 124,417 (155,581 ) (63,418 ) Ending ￦ 302,750 ￦ 766,529 ￦ 78,765 ￦ 1,148,044 Acquisition cost ￦ 302,750 ￦ 1,119,885 ￦ 78,765 ￦ 1,501,400 Less: Accumulated depreciation — ￦ (353,356 ) — ￦ (353,356 ) (In millions of Korean won) 2017 Land Buildings Construction-in- progress Total Acquisition cost ￦ 302,750 ￦ 1,119,885 ￦ 78,765 ￦ 1,501,400 Less: Accumulated depreciation — (353,356 ) — (353,356 ) Beginning 302,750 766,529 78,765 1,148,044 Acquisition — 775 48,075 48,850 Disposal/Abandonment (3,493 ) (6,434 ) — (9,927 ) Depreciation — (47,295 ) — (47,295 ) Transfer from(to) property, plant and equipment 64,449 (1,793 ) (1,184 ) 61,472 Transfer and others (6,916 ) 80,986 (85,683 ) (11,613 ) Ending ￦ 356,790 ￦ 792,768 ￦ 39,973 ￦ 1,189,531 Acquisition cost ￦ 358,358 ￦ 1,191,687 ￦ 39,973 ￦ 1,590,018 Less: Accumulated depreciation (include. Accumulated impairment) (1,568 ) (398,919 ) — (400,487 ) The fair value of investment properties is ￦ ￦ Rental income from investment properties is ￦ ￦ Details of investment properties provided as collateral as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Carrying Secured Related Related Buildings ￦ 711,989 ￦ 98,543 Deposits ￦ 84,334 Land and Buildings ￦ 8,035 ￦ 7,891 Borrowings ￦ 5,260 (In millions of Korean won) 2017 Carrying Secured Related Related Buildings ￦ 772,708 ￦ 104,861 Deposits ￦ 90,150 Land and Buildings ￦ 7,897 ￦ 7,905 Borrowings ￦ 5,270

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2017
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Intangible Assets	12. Intangible Assets Changes in intangible assets for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Goodwill Development 1 Software Frequency usage rights Others Total Acquisition cost 449,379 1,487,420 805,387 2,591,229 1,109,085 6,442,500 Less: Accumulated amortization (including accumulated impairment loss and others) (107,038 ) (1,025,877 ) (574,003 ) (1,618,459 ) (517,372 ) (3,842,749 ) Beginning, net ￦ 342,341 ￦ 461,543 ￦ 231,384 ￦ 972,770 ￦ 591,713 ￦ 2,599,751 Acquisition and capital expenditure — 36,075 35,631 978,309 74,312 1,124,327 Disposal and termination — (8,600 ) (1,928 ) — (16,397 ) (26,925 ) Amortization — (162,682 ) (78,643 ) (273,790 ) (84,606 ) (599,721 ) Impairment (131,600 ) — (46 ) — (3,618 ) (135,264 ) Inclusion in scope of consolidation 42,745 — 2,462 — 16,015 61,222 Others — 8,340 8,278 — (17,205 ) (587 ) Ending, net ￦ 253,486 ￦ 334,676 ￦ 197,138 ￦ 1,677,289 ￦ 560,214 ￦ 3,022,803 Acquisition cost 492,105 1,483,205 838,532 2,531,654 1,154,993 6,500,489 (238,619 ) (1,148,529 ) (641,394 ) (854,365 ) (594,779 ) (3,477,686 ) 2017 (In millions of Korean won) Goodwill Development 1 Software Frequency usage rights Others Total Acquisition cost 492,105 1,483,205 838,532 2,531,654 1,154,993 6,500,489 Less: Accumulated amortization (including accumulated impairment loss and others) (238,619 ) (1,148,529 ) (641,394 ) (854,365 ) (594,779 ) (3,477,686 ) Beginning, net ￦ 253,486 ￦ 334,676 ￦ 197,138 ￦ 1,677,289 ￦ 560,214 ￦ 3,022,803 Acquisition and capital expenditure — 247,863 60,475 — 78,373 386,711 Disposal and termination — (14,806 ) (548 ) — (11,859 ) (27,213 ) Amortization — (151,718 ) (73,174 ) (311,146 ) (99,112 ) (635,150 ) Impairment (84,606 ) — (3 ) — (31,486 ) (116,095 ) Inclusion in scope of consolidation — (332 ) (3,216 ) — (1,374 ) (4,922 ) Others — 2,876 9,569 (1,201 ) (4,674 ) 6,570 Ending, net ￦ 168,880 ￦ 418,559 ￦ 190,241 ￦ 1,364,942 ￦ 490,081 ￦ 2,632,704 Acquisition cost 474,908 1,643,886 893,500 2,530,341 1,171,378 6,714,014 Less; Accumulated amortization (including accumulated impairment loss and others) (306,028 ) (1,225,327 ) (703,259 ) (1,165,399 ) (681,297 ) (4,081,310 ) 1 The Company’s development costs mainly consist of acquisition costs to develop a combined billing system and an information management system. The carrying amount of membership rights with indefinite useful life not subject to amortization is ￦ ￦ Goodwill is allocated to the Group’s cash-generating unit which is identified by operating segments. As of December 31, 2017, goodwill allocated to each cash-generation unit is as follows: (In millions of Korean won) Cash generating Unit Amount Marketing/Customer Telecom Wireless business 1 ￦ 65,057 Finance and Rental BC Card Co., Ltd. 2 41,234 Others PlayD Co., Ltd. (N search Marketing Co., Ltd) 3 42,745 Genie Music Corporation (KT Music Corporation) and others 19,844 Total ￦ 168,880 1 The recoverable amounts of mobile business are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 0.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate -2.46% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 8.95% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on mobile business for the years ended December 31, 2017 and 2016. 2 The recoverable amounts of BC Card Co., Ltd. are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 0.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate 0.11% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 14.62% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on BC Card Co., Ltd. for the years ended December 31, 2017 and 2016. 3 The recoverable amounts of PlayD Co., Ltd. (N search Marketing Co., Ltd.) are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 1.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate 4.27% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 9.5% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on PlayD Co., Ltd. (N search Marketing Co., Ltd.) for the years ended December 31, 2017 and 2016. As a result of the impairment test, the Group recognized the impairment losses of ￦ ￦ The recoverable amounts of Satellite TV segment are calculated based on value-in use calculations or fair value less costs to sell. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 0.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate (-0.77%) based on past performance and its expectation of future market changes. The Group determined cash flow projections based on past performance and its estimation of market growth. Specific risk of related operating segment is reflected in its 13.25% discount rate.

Investments in Associates and J

Investments in Associates and Joint Ventures	12 Months Ended
	Dec. 31, 2017
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Investments in Associates and Joint Ventures	13. Investments in Associates and Joint Ventures Details of associates as of December 31, 2017, are as follows: Percentage of ownership (%) Location Date of 2016 2017 Korea Information & Technology Fund 33.3 % 33.3 % Korea 31-Dec KT-SB Venture Investment 1 50.0 % 50.0 % Korea 31-Dec Mongolian Telecommunications 1 40.0 % — Mongolia 31-Dec KT Wibro Infra Co., Ltd. 26.2 % — Korea 31-Dec KT-IBKC Future Investment Fund 1 1 50.0 % 50.0 % Korea 31-Dec KT-CKP New Media Investment Fund 49.7 % 49.7 % Korea 31-Dec K Bank Inc. 1 — 10.0 % Korea 31-Dec 1 At the end of the reporting period, even though the Group (KT-SB Venture Investment Fund and KT-IBKC Future Investment Fund 1) has 50% ownership, the equity method of accounting has been applied as the Group, which is a limited partner of investment fund, cannot participate in determining the operating and financial policies. As of December 31, 2017, the entire shares of Mongolian Telecommunications is classified as assets held for sale, and KT Wibro Infra Co., Ltd. was liquidated during 2017. Also, 8% of non-voting convertible stock are excluded from percentage of ownership for K bank Inc. Changes in investments in associates and joint ventures for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Beginning Acquisition Share of net profit 1 Impairment Others Ending Korea Information & Technology Fund ￦ 127,583 ￦ — ￦ 7,446 ￦ — ￦ (60 ) ￦ 134,969 KT-SB Venture Investment 4,861 — (125 ) — — 4,736 Mongolian Telecommunications 7,483 — 32 — (1,271 ) 6,244 KT Wibro Infra Co., Ltd. 69,328 — — (17,128 ) — 52,200 KT-CKP New Media Investment Fund 3,860 — 594 — — 4,454 Others 56,914 29,052 (5,400 ) — 906 81,472 ￦ 270,029 ￦ 29,052 ￦ 2,547 ￦ (17,128 ) ￦ (425 ) ￦ 284,075 2017 (In millions of Korean won) Beginning Acquisition Share of net profit 1 Impairment Others Ending Korea Information & Technology Fund ￦ 134,969 ￦ — ￦ 4,275 ￦ — ￦ 290 ￦ 139,534 KT-SB Venture Investment 4,736 (1,069 ) (725 ) — — 2,942 Mongolian Telecommunications 6,244 — (348 ) — (5,896 ) — KT Wibro Infra Co., Ltd. 52,200 (52,200 ) — — — — KT-IBKC Future Investment Fund 1 3,621 7,500 (296 ) — — 10,825 KT-CKP New Media Investment Fund 4,454 (2,970 ) 810 — — 2,294 K Bank Inc. — 26,543 (17,244 ) — 32,809 42,108 Others 77,851 3,178 (1,952 ) (3,662 ) 6,313 81,728 ￦ 284,075 ￦ (19,018 ) ￦ (15,480 ) ￦ (3,662 ) ￦ 33,516 ￦ 279,431 1 KT investment Co., Ltd., a subsidiary of the Group, recognized its share in net profit from associates and joint ventures as operating revenue and expense. These include its share in gain from associates and joint ventures of ￦ ￦ Summarized financial information of associates and joint ventures as of and for the years ended December 31, 2016 and 2017, is as follows: (In millions of Korean won) 2016 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 154,651 ￦ 250,257 ￦ — ￦ — KT-SB Venture Investment 1,009 8,704 242 — Mongolian Telecommunications 9,852 9,055 3,296 — KT Wibro Infra Co., Ltd. 274,811 6 4,996 52 KT-CKP New Media Investment Fund 1,801 7,170 4 — (In millions of Korean won) 2016 Operating Profit (loss) Other Total Dividend Korea Information & Technology Fund ￦ 26,942 ￦ 22,338 ￦ (9,425 ) ￦ 12,913 ￦ 3,201 KT-SB Venture Investment 2 (251 ) — (251 ) — Mongolian Telecommunications 10,336 81 3,178 3,259 — KT Wibro Infra Co., Ltd. 391 5,025 — 5,025 — KT-CKP New Media Investment Fund 1,684 1,195 — 1,195 — (In millions of Korean won) 2017 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 144,874 ￦ 273,727 ￦ — ￦ — KT-SB Venture Investment 120 5,770 6 — KT-IBKC Future Investment Fund 1 5,499 16,302 152 — KT-CKP New Media Investment Fund 287 4,333 — — K Bank Inc. 1,258,969 92,137 1,116,154 1,177 (In millions of Korean won) 2017 Operating Profit (loss) Other Total Dividend Korea Information & Technology Fund ￦ 36,462 ￦ 12,825 ￦ 1,868 ￦ 14,693 ￦ 739 KT-SB Venture Investment 3 (1,449 ) — (1,449 ) — KT-IBKC Future Investment Fund 1 15 (593 ) — (593 ) — KT-CKP New Media Investment Fund 1,593 1,632 — 1,632 — K Bank Inc. 20,926 (83,787 ) (746 ) (84,533 ) — Details of a reconciliation of the summarized financial information to the carrying amount of interests in the associates and joint ventures as of and for the years end December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Net assets Percentage of Share in net Intercompany Carrying Korea Information & Technology Fund ￦ 404,908 33.3 % ￦ 134,969 ￦ — ￦ 134,969 KT-SB Venture Investment 9,471 50.0 % 4,736 — 4,736 Mongolian Telecommunications 15,610 40.0 % 6,244 — 6,244 KT Wibro Infra Co., Ltd. 269,769 26.2 % 70,679 (18,479 ) 52,200 KT-CKP New Media Investment Fund 8,967 49.7 % 4,454 — 4,454 2017 (In millions of Korean won) Net assets Percentage of Share in net Intercompany Carrying Korea Information & Technology Fund ￦ 418,601 33.3 % ￦ 139,534 ￦ — ￦ 139,534 KT-SB Venture Investment 5,884 50.0 % 2,942 — 2,942 KT-IBKC Future Investment Fund 1 21,649 50.0 % 10,825 — 10,825 KT-CKP New Media Investment Fund 4,620 49.7 % 2,294 — 2,294 K Bank Inc. 1 233,775 10.0 % 42,108 — 42,108 1 8% of non-voting convertible stock are excluded from percentage of ownership for K bank Inc Due to discontinuance of equity method of accounting, the Group has not recognized loss from associates and joint ventures of ￦ ￦ ￦ ￦ ￦ ￦

Trade and other payables

Trade and other payables	12 Months Ended
	Dec. 31, 2017
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Trade and other payables	14. Trade and other payables Details of trade and other payables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) December 31, 2016 December 31, 2017 Current liabilities Trade payables ￦ 1,235,955 ￦ 1,399,287 Other payables 5,903,816 6,024,847 Total ￦ 7,139,771 ￦ 7,424,134 Non-current liabilities Trade payables ￦ 8,041 ￦ 4,787 Other payables 1,180,270 996,582 Total ￦ 1,188,311 ￦ 1,001,369 Details of other payables as of December 31, 2016 and 2017 are as follows: (In millions of Korean won) 2016 2017 Non-trade payables 1 ￦ 4,803,642 ￦ 4,773,223 Accrued expenses 1,061,002 1,011,089 Operating deposits 861,739 850,999 Others 357,703 386,118 Less: non-current (1,180,270 ) (996,582 ) Current ￦ 5,903,816 ￦ 6,024,847 1 Settlement payables of BC Card Co., Ltd. of ￦ ￦

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
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Borrowings	15. Borrowings Details of borrowings as of December 31, 2016 and 2017, are as follows: Debentures (In millions of Korean won and thousands of foreign currencies) 2016 2017 Type Maturity Annual interest Foreign currency Korean won Foreign currency Korean won MTNP notes 1 Sept. 07, 2034 6.50% USD 100,000 ￦ 120,850 USD 100,000 ￦ 107,140 MTNP notes Jan. 20, 2017 — USD 350,000 422,975 — — FR notes 2 Aug. 28, 2018 LIBOR(3M)+1.15% USD 300,000 362,550 USD 300,000 321,420 MTNP notes Apr. 22, 2017 — USD 650,000 785,525 — — MTNP notes Apr. 22, 2019 2.63% USD 350,000 422,975 USD 350,000 374,990 MTNP notes Jan. 29, 2018 0.86% JPY 6,800,000 70,503 JPY 6,800,000 64,539 MTNP notes Feb. 23, 2018 0.48% JPY 15,000,000 155,522 JPY 15,000,000 142,367 MTNP notes July 18, 2026 2.50% USD 400,000 483,400 USD 400,000 428,560 MTNP notes Aug 07, 2022 2.63% — — USD 400,000 428,560 The 173-2nd Public bond Aug. 06, 2018 6.62% — 100,000 — 100,000 The 177-3rd Public bond Feb. 09, 2017 — — 170,000 — — The 179th Public bond Mar. 29, 2018 4.47% — 260,000 — 260,000 The 180-2nd Public bond Apr. 26, 2021 4.71% — 380,000 — 380,000 The 181-2nd Public bond Aug. 26, 2018 3.99% — 90,000 — 90,000 The 181-3rd Public bond Aug. 26, 2021 4.09% — 250,000 — 250,000 The 182-2nd Public bond Oct. 28, 2021 4.31% — 100,000 — 100,000 The 183-2nd Public bond Dec. 22, 2021 4.09% — 90,000 — 90,000 The 183-3rd Public bond Dec. 22, 2031 4.27% — 160,000 — 160,000 The 184-1st Public bond Apr. 10, 2018 2.74% — 120,000 — 120,000 The 184-2nd Public bond Apr. 10, 2023 2.95% — 190,000 — 190,000 The 184-3rd Public bond Apr. 10, 2033 3.17% — 100,000 — 100,000 The 185-1st Public bond Sept. 16, 2018 3.46% — 200,000 — 200,000 The 185-2nd Public bond Sept. 16, 2020 3.65% — 300,000 — 300,000 The 186-1st Public bond June 26, 2017 — — 120,000 — — The 186-2nd Public bond June 26, 2019 3.08% — 170,000 — 170,000 The 186-3rd Public bond June 26, 2024 3.42% — 110,000 — 110,000 The 186-4th Public bond June 26, 2034 3.70% — 100,000 — 100,000 The 187-1st Public bond Sept. 02, 2017 — — 110,000 — — The 187-2nd Public bond Sept. 02, 2019 2.97% — 220,000 — 220,000 The 187-3rd Public bond Sept. 02, 2024 3.31% — 170,000 — 170,000 The 187-4th Public bond Sept. 02, 2034 3.55% — 100,000 — 100,000 The 188-1st Public bond Jan. 29, 2020 2.26% — 160,000 — 160,000 The 188-2nd Public bond Jan. 29, 2025 2.45% — 240,000 — 240,000 The 188-3rd Public bond Jan. 29, 2035 2.71% — 50,000 — 50,000 The 189-1st Public bond Jan. 27, 2019 1.76% — 100,000 — 100,000 The 189-2nd Public bond Jan. 27, 2021 1.95% — 130,000 — 130,000 The 189-3rd Public bond Jan. 27, 2026 2.20% — 100,000 — 100,000 The 189-4rd Public bond Jan. 27, 2036 2.35% — 70,000 — 70,000 The 17th unsecured bond Apr. 22, 2018 1.89% — 60,000 — 60,000 7,344,300 5,987,576 Less: Current portion (1,607,570 ) (1,357,776 ) Discount on bonds (20,852 ) (19,347 ) Total ￦ 5,715,878 ￦ 4,610,453 1 As of December 31, 2017, the Controlling Company has outstanding notes in the amount of USD 100 million with fixed interest rates under Medium Term Note Program (“MTNP”) registered in the Singapore Stock Exchange, which allowed issuance of notes of up to USD 2,000 million. However, the MTN Program has been suspended since 2007. 2 Libor (3M) are approximately 1.695 % as of December 31, 2017. Short-term borrowings (In millions of Korean won) 2016 2017 Type Financial institution Annual interest rates Operational Shinhan Bank 2.99% ~ 4.41% ￦ 120,300 ￦ 113,300 Standard Charted Bank — 8,000 — Korea Development Bank 3.97% 20,800 12,000 Indutrial Bank of Korea — 1,000 — SooHyup Bank 4.22% 3,000 3,000 Total ￦ 153,100 ￦ 128,300 Long-term borrowings (In millions of Korean won and thousands of foreign currencies) 2016 2017 Financial institution Type Annual interest rates Foreign currency Korean won Foreign currency Korean won Export-Import Bank of Korea Inter-Korean Cooperation Fund 1 1.50% — ￦ 5,181 — ￦ 4,688 Shinhan Bank General loans 2.50% — 31,000 — 30,000 Facility loans 2.56% — 6,493 — 6,000 Vessel facility loans 2 LIBOR(3M)+0.706% USD 21,000 25,379 USD 15,000 16,071 KEB Hana Bank General loans 3.95% — 3,000 — 3,000 Standard Charted Bank General loans 3.16% — — — 8,000 Woori Bank General loans — — 13,000 — — NongHyup Bank General loans 2.86% — — — 8,000 Facility loans 2.00% 123 — 123 Korea Development Bank General loans 3.27% — 30,000 — 30,000 Kookmin Bank Facility loans 2.59% — 7,000 — 2,333 NH Investment & Security Co., Ltd. Commercial papers 3.17% — 300,000 — 300,000 Others Redeemable convertible preferred stock 3 — — 950 — 950 Kookmin Bank and other 2 3.15% USD 183,796 222,117 USD 166,108 177,968 ￦ 644,243 ￦ 587,133 Less: Current portion ￦ (59,331 ) ￦ (87,398 ) Total ￦ 584,912 ￦ 499,735 1 The Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period. 2 LIBOR(3M) is approximately 1.695% as of December 31, 2017. 3 Skylife TV Co., Ltd., a subsidiary of the Group, issued 1,900,000 of redeemable convertible preferred stock with a par value per share of ￦ Repayment schedule of the Group’s borrowings including the portion of current liabilities as of December 31, 2017, is as follows: (in millions of Korean won) Debentures Borrowings Total In local In foreign Sub- total In local In foreign Sub- total Jan 1, 2018 ~ Dec 31, 2018 ￦ 830,000 ￦ 528,326 ￦ 1,358,326 ￦ 167,395 ￦ 48,303 ￦ 215,698 ￦ 1,574,024 Jan 1, 2019 ~ Dec 31, 2019 490,000 374,990 864,990 343,465 48,303 391,768 1,256,758 Jan 1, 2020 ~ Dec 31, 2020 460,000 — 460,000 1,518 45,089 46,607 506,607 Jan 1, 2021 ~ Dec 31, 2021 950,000 — 950,000 1,518 41,875 43,393 993,393 After 2022 1,390,000 964,260 2,354,260 7,498 10,469 17,967 2,372,227 ￦ 4,120,000 ￦ 1,867,576 ￦ 5,987,576 ￦ 521,394 ￦ 194,039 ￦ 715,433 ￦ 6,703,009 Carrying amount and fair value of the Group’s debentures and borrowings as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Type Carrying Amount Fair Value Carrying Amount Fair Value Debentures ￦ 7,323,448 ￦ 7,387,085 ￦ 5,968,229 ￦ 6,022,551 Long-term borrowings (Including current portion of long-term borrowings) 644,243 644,010 587,133 587,475 Short-term borrowings 153,100 153,100 128,300 128,300 Total ￦ 8,120,791 ￦ 8,184,195 ￦ 6,683,662 ￦ 6,738,326 The fair values of debentures and long-term borrowings are calculated by discounting the expected future cash flows at weighted average borrowing rate. The weighted average borrowing rate is approximately 3.37% (2016: 3.38%) as of December 31, 2017. The carrying amount of borrowings of subsidiaries is the reasonable approximately amount of the fair value.

Provisions

Provisions	12 Months Ended
	Dec. 31, 2017
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Provisions	16. Provisions Changes in provisions for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 17,524 ￦ 91,827 ￦ 85,921 ￦ 195,272 Increase (transfer) 3,392 13,653 40,293 57,338 Usage (640 ) (3,378 ) (37,378 ) (41,396 ) Reversal (1,238 ) (790 ) (12,007 ) (14,035 ) Ending balance ￦ 19,038 ￦ 101,312 ￦ 76,829 ￦ 197,179 Current 18,988 2,334 75,163 96,485 Non-current 50 98,978 1,666 100,694 2017 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 19,038 ￦ 101,312 ￦ 76,829 ￦ 197,179 Increase (Transfer) 3,842 2,827 41,550 48,219 Usage (1,740 ) (2,178 ) (22,382 ) (26,300 ) Reversal (2,834 ) (1,723 ) (11,467 ) (16,024 ) Change in scope of consolidation — (22 ) (22 ) (44 ) Ending balance ￦ 18,306 ￦ 100,216, ￦ 84,508 ￦ 203,030 Current 17,238 1,766 59,168 78,172 Non-current 1,068 98,450 25,340 124,858

Net Defined Benefit Liabilities

Net Defined Benefit Liabilities	12 Months Ended
	Dec. 31, 2017
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Net Defined Benefit Liabilities	17. Net Defined Benefit Liabilities The amounts recognized in the statements of financial position are determined as follows: (in millions of Korean won) 2016 2017 Present value of defined benefit obligations ￦ 1,713,184 ￦ 1,911,166 Fair value of plan assets (1,334,780 ) (1,519,779 ) Liabilities ￦ 378,404 ￦ 396,079 Assets in the statement of financial position ￦ — ￦ 3,692 Changes in the defined benefit obligations for the years ended December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Beginning ￦ 1,601,974 ￦ 1,713,184 Current service cost 205,114 210,336 Interest expense 37,378 38,994 Benefit paid (127,581 ) (154,600 ) Changes due to settlements of plan (424 ) (61 ) Remeasurements: Actuarial gains and losses arising from changes in demographic assumptions (53,407 ) 3,353 Actuarial gains and losses arising from changes in financial assumptions 26,717 36,946 Actuarial gains and losses arising from experience adjustments 18,809 63,583 Changes in scope of Consolidation 4,604 (569 ) Ending ￦ 1,713,184 ￦ 1,911,166 Changes in the fair value of plan assets for the years ended December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Beginning ￦ 1,077,891 ￦ 1,334,780 Interest income 25,237 30,303 Remeasurements: Return on plan assets (excluding amounts included in interest income) (2,323 ) (5,557 ) Benefits paid (88,876 ) (130,510 ) Employer contributions 322,851 290,895 Changes in scope of consolidation — (132 ) Ending ￦ 1,334,780 ￦ 1,519,779 For the year ended December 31, 2018, reasonable estimation for expected employer contributions is ￦ Amounts recognized in the statement of profit or loss for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Current service cost ￦ 200,994 ￦ 205,114 ￦ 210,336 Net Interest cost 16,793 12,141 8,691 Past service cost — 424 (61 ) Transfer out (11,942 ) (8,737 ) (9,196 ) Transfer to discontinued operation (3,031 ) — — Total expenses ￦ 202,814 ￦ 208,942 ￦ 209,770 Principal actuarial assumptions used are as follows: 2015.12.31 2016.12.31 2017.12.31 Discount rate 2.43 % 2.43 % 2.76 % Future salary increase 4.06 % 4.10 % 4.51 % The sensitivity of the defined benefit obligations as of December 31, 2017, to changes in the principal assumptions is: (in percentage, in millions of Korean won ) Effect on defined benefit obligation Changes in Increase in Decrease in Discount rate 0.5% point ￦ (62,000 ) ￦ 76,560 Salary growth rate 0.5% point 71,273 (57,848 ) A decrease in corporate bond yields will increase plan liabilities, although this will be partially offset by an increase in the value of the plans’ bond holdings. The above sensitivity analyses are based on an assumption while holding all other assumptions constant. In practice, this is unlikely to occur, and changes in some of the assumptions may be correlated. The sensitivity of the defined benefit obligation to changes in principal actuarial assumptions is calculated using the projected unit credit method, the same method applied when calculating the defined benefit obligations recognized on the statement of financial position. The Group actively monitors how the duration and the expected yield of the investments match the expected cash outflows arising from the pension obligations. Expected contributions to post-employment benefit plans for the year ending December 31, 2018, are ￦ The expected maturity analysis of undiscounted pension benefits as at December 31, 2017, is as follows: (in millions of Korean won) Less than 1 year Between 1-2 Between 2-5 Over 5 years Total Pension benefits ￦ 142,963 ￦ 179,612 ￦ 627,302 ￦ 3,763,601 ￦ 4,713,478 The weighted average duration of the defined benefit obligations is 7.6 years.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2017
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Defined Contribution Plan	18. Defined Contribution Plan Recognized expense related to the defined contribution plan for the year ended December 31, 2017, is ￦ ￦ ￦

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
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Commitments and Contingencies	19. Commitments and Contingencies As of December 31, 2017, major commitments with local financial institutions are as follows: (In millions of Korean won and foreign currencies in thousands) Financial institution Currency Limit Used amount Bank overdraft Kookmin Bank and others KRW 1,730,000 72 Commercial papers NH Investment & Securities KRW 370,000 300,000 Collateralized loan on accounts receivable-trade NongHyup Bank and others KRW 35,560 — Collateralized loan on electronic accounts receivable-trade Shinhan Bank and others KRW 343,000 42,350 Plus electronic notes payable Industrial Bank of Korea KRW 50,000 140 Loans for working capital Korea Development Bank KRW 306,500 207,300 Green energy factoring Shinhan Bank KRW 16 16 FX forward trading commitment Shinhan Bank USD 11,500 — Facility loans Kookmin Bank and others KRW 8,456 8,456 USD 212,000 166,108 Facility loans on ships Shinhan Bank USD 30,000 15,000 Inter-Korean Cooperation Fund Export-Import Bank of Korea KRW 37,700 4,688 Total KRW 2,881,232 563,022 USD 253,500 181,108 As of December 31, 2017, guarantees received from financial institutions are as follows: (In millions of Korean won and thousands of foreign currencies) Financial institution Currency Limit Performance guarantee Seoul Guarantee Insurance and others KRW 116,787 USD 1,275 Guarantee for import letters of credit Industrial Bank of Korea and others USD 5,980 Guarantee for payment in foreign currency KEB Hana and others USD 54,072 PLN 1 23,000 Guarantee for advances received Export-Import Bank of Korea USD 7,414 Comprehensive credit line KEB Hana Bank and others KRW 55,000 Bid guarantee KEB Hana Bank USD 400 Bid guarantee Korea Software Financial Cooperative KRW 96,911 Performance guarantee /Warranty Guarantee KRW 302,062 Guarantee for advances received/others Korea Software Financial Cooperative KRW 99,228 Warranty guarantee Seoul Guarantee Insurance KRW 2,962 Guarantees for licensing KRW 4,077 Guarantees for public sale KRW 50 Guarantees for deposits Seoul Guarantee Insurance and others KRW 4,203 Total KRW 681,280 USD 69,141 PLN 1 23,000 1 Polish Zloty. As of December 31, 2017, guarantees provided by the Group to a third party, are as follows: (in millions of Korean won) Subject to payment guarantees Creditor Limit Used amount Period KT Estate Inc. Busan Gaya Centreville Buyers Shinhan ￦ ￦ Nov 10, 2017 ~Oct. 31, 2020 KT Estate Inc. Daegu Beomeo -Crossroads Shinhan 81,722 14,237 Oct 29, 2017 ~Nov. 30, 2020 KT Hitel Co., Ltd. KEB Hana Bank Cash 384 — Apr 19, 2017 ~ Apr 19, 2018 The Controlling Company is jointly and severally obligated with KT Sat Co., Ltd. to pay KT Sat Co., Ltd.’s liabilities prior to spin-off. As of December 31, 2017, the Controlling Company and KT Sat Co., Ltd. are jointly and severally liable for reimbursement of ￦ For the year ended December 31, 2017, the Group entered into agreements with GIGA LTE Thirty-first to Thirty-sixth Securitization Specialty Co., Ltd. and KT M Mobile 1st Securitization Specialty Co., Ltd. (2016: Olleh KT Twenty-fifth to Twenty-sixth Securitization Specialty Co., Ltd. and GIGA LTE Twenty-seventh to Thirtieth Securitization Specialty Co., Ltd.), and disposed its trade receivables related to handset sales. The Group also made asset management agreements with each securitization specialty company and will receive the related management fees. As of December 31, 2017, the Group is a defendant in 187 lawsuits with an total claims of ￦ ￦ ￦ On December 24, 2013, Asia Broadcast Satellite Holdings Ltd. (“ABS”) filed a request for arbitration with the International Centre for Dispute Resolution of the American Arbitration Association for the compensation of damages from the relocation of the ground equipment and the alleged breach of the entrustment control contract related to the satellite Koreasat-3, which was made and entered into with the Controlling Company and its subsidiary, KT Sat Co., Ltd. Subsequently on December 31, 2013, ABS filed another request for arbitration with the International Court of Arbitration of the International Chamber of Commerce (ICC) for the claim on the ownership of the satellite Koreasat-3 and compensation for the damages from the alleged breach of the sales contract entered into with the Controlling Company and its subsidiary, KT Sat Co., Ltd. These two cases were combined by the ICC to be treated as a single case for the arbitration. On July 18, 2017, the ICC issued a partial ruling in favor of ABS that ABS has the ownership right to the Koreasat-3 satellite. Following the ruling, on October 12, 2017, the Controlling Company and KT Sat Co., Ltd., as joint defendants to the arbitration, filed a lawsuit for cancellation of the arbitration ruling at the New York Court of Appeals in the United States. On March 9, 2018, the ICC made the final ruling in favor of ABS that the Controlling Company and KT Sat Co., Ltd. should compensate ABS for the damage of $748,564 and the accumulated interest of $287,673.15 for the period from December 1, 2013 to March 9, 2018, and the interest for delay at 9% per annum. As the final ruling by the ICC was based on the presumption that the partial ruling that the satellite belongs to ABS is valid, the Controlling Company and KT Sat Co., Ltd. are contemplating to file an additional appeal for the arbitration rulings at the New York Court of Appeals. At the end of the current reporting period, the final outcome of these claims cannot be reasonably estimated. According to the financial and other covenants included in certain debentures and borrowings, the Group is required to maintain certain financial ratios such as debt-to-equity ratio, use the funds for the designated purpose and report to the creditors periodically. The covenant also contains restriction on provision of additional collateral and disposal of certain assets. At the end of the reporting period, the Group is offering construction completion guarantee agreement to development of Nonsan Hwagidong apartment complex. If a contingent event occurs in between November 24, 2017 and to August 9, 2019, the Group collaterally guarantees the debt of AbleNS 1st Co. up to ￦ At the end of the reporting period, the Group participates in Algerie Sidi Abdela new town development consortium (percentage ownership: 2.5%) and has joint liability with other consortium participants. At the end of the reporting period, contract amount of property, plant and equipment acquisition agreement made but not yet recognized as liabilities amounts to ￦ ￦

Lease

Lease	12 Months Ended
	Dec. 31, 2017
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Lease	20. Lease The Group’s non-cancellable lease arrangements are as follows: The Group as the Lessee Finance Lease Details of finance lease assets as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Acquisition costs ￦ 298,631 ￦ 325,975 Less: Accumulated depreciation (105,013 ) (126,091 ) Net balance ￦ 193,618 ￦ 199,884 As of December 31, 2017, the Group recognized financial lease assets as other property and equipment. The related depreciation amounted to ￦ ￦ Details of future minimum lease payments As of December 31, 2016 and 2017, under finance lease contracts are summarized below: (in millions of Korean won) 2016 2017 Total amount of minimum lease payments Within one year ￦ 79,644 ￦ 88,441 From one year to five years 131,813 132,113 More than five years — 81 211,457 220,635 Unrealized interest expense 30,743 43,758 Net amount of minimum lease payments Within one year 64,008 68,651 From one year to five years 116,706 108,146 More than five years — 80 Total ￦ 180,714 ￦ 176,877 Operating Lease Details of future minimum lease payments As of December 31, 2016 and 2017, under operating lease contracts are summarized below: (in millions of Korean won) 2016 2017 Within one year ￦ 102,015 ￦ 109,258 From one year to five years 270,462 266,434 Thereafter 16,549 1,635 Total ￦ 389,026 ￦ 377,327 Operating lease expenses incurred for the years ended December 31, 2015, 2016 and 2017, amounted to ￦ ￦ ￦

Share Capital

Share Capital	12 Months Ended
	Dec. 31, 2017
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Share Capital	21. Share Capital As of December 31, 2016 and 2017, the Group’s number of authorized shares is one billion. 2016 2017 Number of outstanding Par value per share (Korean won) Ordinary Shares (in millions of Korean won) Number of outstanding Par value per share (Korean won) Ordinary Shares (in millions of Korean won) Ordinary shares 1 261,111,808 ￦ 5,000 ￦ 1,564,499 261,111,808 ￦ 5,000 ￦ 1,564,499 1 The Group retired 51,787,959 treasury shares against retained earnings. Therefore, the ordinary shares amount differs from the amount resulting from multiplying the number of shares issued by ￦

Retained Earnings

Retained Earnings	12 Months Ended
	Dec. 31, 2017
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Retained Earnings	22. Retained Earnings Details of retained earnings as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Legal reserve 1 ￦ 782,249 ￦ 782,249 Voluntary reserves 2 4,651,362 4,651,362 Unappropriated retained earnings 4,210,872 4,393,315 Total ￦ 9,644,483 ￦ 9,826,926 1 The Commercial Code of the Republic of Korea requires the Group to appropriate, as a legal reserve, an amount equal to a minimum of 10% of cash dividends paid until such reserve equals 50% of its issued capital stock. The reserve is not available for the payment of cash dividends, but may be transferred to capital stock with the approval of the Group’s Board of Directors or used to reduce accumulated deficit, if any, with the ratification of the Group’s majority shareholders. 2 The provision of research and development of human is separately accumulated with tax reserve fund during earned surplus disposal by Tax Reduction and Exemption Control Act of Korea. Reversal of this provision can be paid out as dividends according to related tax law.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income and Other Components of Equity	12 Months Ended
	Dec. 31, 2017
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Accumulated Other Comprehensive Income and Other Components of Equity	23. Accumulated Other Comprehensive Income and Other Components of Equity As of December 31, 2016 and 2017, the details of the Controlling Company’s accumulated other comprehensive income are as follows: (in millions of Korean won) 2016 2017 Changes in investments in associates and joint ventures ￦ (10,883 ) ￦ (735 ) Loss on derivatives valuation (34,309 ) (3,463 ) Gain of valuation on available-for-sale 54,106 52,673 Foreign currency translation adjustment (10,346 ) (17,490 ) Total ￦ (1,432 ) ￦ 30,985 Changes in accumulated other comprehensive income for the years ended December 31, 2016 and 2017, are as follows: 2016 (in millions of Korean won) Beginning Increase Reclassified to Ending Changes in investments in associates and ￦ (10,312 ) ￦ (571 ) ￦ — ￦ (10,883 ) Gain or loss on derivatives valuation (23,234 ) 64,796 (75,871 ) (34,309 ) Gain or loss of valuation on available-for-sale 52,415 5,204 (3,513 ) 54,106 Foreign currency translation adjustment (4,999 ) (5,347 ) — (10,346 ) Total ￦ 13,870 ￦ 64,082 ￦ (79,384 ) ￦ (1,432 ) 2017 (in millions of Korean won) Beginning Increase Reclassified to Ending Changes in investments in associates and ￦ (10,883 ) ￦ 10,148 ￦ — ￦ (735 ) Gain or loss on derivatives valuation (34,309 ) (111,083 ) 141,929 (3,463 ) Gain or loss of valuation on available-for-sale 54,106 54,017 (55,450 ) 52,673 Foreign currency translation adjustment (10,346 ) (7,144 ) — (17,490 ) Total ￦ (1,432 ) ￦ (54,062 ) ￦ 86,479 ￦ 30,985 As of December 31, 2016 and 2017, the other components of equity are as follows: (in millions of Korean won) 2016 2017 Treasury stock 1 ￦ (859,789 ) ￦ (853,108 ) Loss on disposal of treasury stock 2 607 873 Share-based payments 5,762 6,483 Others 3 (364,514 ) (359,550 ) Total ￦ (1,217,934 ) ￦ (1,205,302 ) 1 During the year ended December 31, 2017, the Group granted 125,412 treasury shares as share-based payment. 2 The amount directly reflected in equity is ￦ ￦ 3 Profit or loss incurred from transactions with non-controlling As of December 31, 2016 and 2017, the details of treasury stock are as follows: 2016 2017 Number of shares 16,140,165 16,014,753 Amounts (In millions of Korean won) ￦ 859,789 ￦ 853,108 Treasury stock is expected to be used for the stock compensation for the Group’s directors and employees and other purposes.

Share-based Payments

Share-based Payments	12 Months Ended
	Dec. 31, 2017
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Share-based Payments	24. Share-based Payments Details of share-based payments as of December 31, 2017, are as follows: 11th Grant date July 27, 2017 Grantee CEO, inside directors, outside directors, executives Vesting conditions Service condition: 1 year Non-market Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) After July 27, 2018 Valuation method Fair value method Changes in the number of stock options and the weighted-average exercise price as of December 31, 2016 and 2017, are as follows: 2016 Beginning Granted Expired Forfeited Exercised 1 Ending Number of 9th grant ￦ 263,123 ￦ 54,913 ￦ 181,685 ￦ — ￦ 136,351 ￦ — ￦ — 10th grant — 318,506 — — — 318,506 — Total ￦ 263,123 ￦ 373,419 ￦ 181,685 ￦ — ￦ 136,351 ￦ 318,506 ￦ — 2017 Beginning Granted Expired Forfeited Exercised 1 Ending Number of 10th grant ￦ 318,506 ￦ — ￦ 193,094 ￦ — ￦ 125,412 ￦ — ￦ — 11th grant — 316,949 — — — 316,949 — Total ￦ 318,506 ￦ 316,949 ￦ 193,094 ￦ — ￦ 125,412 ￦ 316,949 ￦ — 1 The weighted average price of ordinary shares at the time of exercise during 2017 was ￦ ￦

Operating Revenues

Operating Revenues	12 Months Ended
	Dec. 31, 2017
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Operating Revenues	25. Operating Revenues Operating revenues for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Services provided ￦ 19,455,693 ￦ 19,935,865 ￦ 19,898,725 Sale of goods 2,755,980 2,819,141 3,360,816 Others 488,183 365,872 287,388 Total ￦ 22,699,856 ￦ 23,120,878 ￦ 23,546,929

Operating Expenses

Operating Expenses	12 Months Ended
	Dec. 31, 2017
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Operating Expenses	26. Operating Expenses Operating expenses for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Salaries and wages ￦ 3,303,484 ￦ 3,477,596 ￦ 3,568,456 Depreciation 2,756,131 2,762,773 2,745,969 Amortization of intangible assets 582,467 582,493 618,533 Commissions 1,036,852 1,099,429 1,085,865 Interconnection charges 689,293 690,285 640,612 International interconnection fee 231,060 216,633 214,058 Purchase of inventories 3,963,036 3,407,263 4,053,693 Changes of inventories (198,028 ) 162,323 (187,439 ) Sales commission 1,856,595 1,968,035 2,201,778 Service cost 1,163,887 1,322,337 1,428,405 Utilities 319,303 323,406 323,313 Taxes and dues 256,958 255,480 279,574 Rent 469,950 455,457 448,772 Insurance premium 211,104 178,231 69,384 Installation fee 249,413 156,669 146,783 Advertising expenses 177,348 185,560 197,114 Research and development expenses 183,821 167,881 168,635 Card service cost 2,959,765 3,049,559 3,094,894 Others 1,410,349 1,319,688 1,379,438 Total ￦ 21,622,788 ￦ 21,781,098 ￦ 22,477,837 Details of employee benefits for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Short-term employee benefits ￦ 3,055,699 ￦ 3,206,904 ￦ 3,297,944 Post-employment benefits(Defined benefit plan) 202,814 208,942 209,770 Post-employment benefits(Defined contribution plan) 35,699 46,023 45,936 Post-employment benefits(Others) 5,535 8,017 6,949 Share-based payment 3,737 7,710 7,660 Total ￦ 3,303,484 ￦ 3,477,596 ￦ 3,568,259

Financial Income and Costs

Financial Income and Costs	12 Months Ended
	Dec. 31, 2017
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Financial Income and Costs	27. Financial Income and Costs Details of financial income for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Interest income ￦ 70,035 ￦ 115,686 ￦ 93,078 Gain on foreign currency transactions 18,766 24,915 79,653 Gain on foreign currency translation 11,280 12,165 225,580 Gain on settlement of derivatives 368 8,515 — Gain on valuation of derivatives 141,512 109,436 57 Others 30,899 25,422 7,960 Total ￦ 272,860 ￦ 296,139 ￦ 406,328 Details of financial expenses for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Interest expenses ￦ 385,925 ￦ 337,219 ￦ 302,464 Loss on foreign currency transactions 42,831 37,936 40,303 Loss on foreign currency translation 175,613 121,949 12,239 Loss on settlement of derivatives 6,280 632 58,569 Loss on valuation of derivatives 1,733 138 209,582 Loss on disposal of trade receivables 2,539 15,838 20,355 Impairment loss on available-for-sale 1,805 966 9 Others 28,605 409 1,010 ￦ 645,331 ￦ 515,087 ￦ 644,531

Deferred Income Tax and Income

Deferred Income Tax and Income Tax Expense	12 Months Ended
	Dec. 31, 2017
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Deferred Income Tax and Income Tax Expense	28. Deferred Income Tax and Income Tax Expense The analysis of deferred tax assets and deferred tax liabilities as of December 31, 2016 and 2017, is as follows: (In millions of Korean won) 2016 2017 Deferred tax assets Deferred tax assets to be recovered within 12 months ￦ 265,997 ￦ 318,339 Deferred tax assets to be recovered after 1,124,420 1,140,252 ￦ 1,390,417 ￦ 1,458,591 Deferred tax liabilities Deferred tax liability to be recovered within 12 months (48,033 ) (15,705 ) Deferred tax liability to be recovered after (778,655 ) (859,126 ) (826,688 ) (874,831 ) Deferred tax assets after offsetting ￦ 701,409 ￦ 712,222 Deferred tax liabilities after offsetting ￦ 137,680 ￦ 128,462 The gross movements on the deferred income tax account for the years ended December 31, 2016 and 2017, are calculated as follows: (In millions of Korean won) 2016 2017 Beginning ￦ 715,747 ￦ 563,729 Charged(credited) to the statement of profit or loss (152,102 ) (1,771 ) Charged(credited) to other 84 21,802 Ending ￦ 563,729 ￦ 583,760 The movement in deferred income tax assets and liabilities during the year, without taking into consideration the offsetting of balances within the same tax jurisdiction, is as follows: (In millions of Korean won) 2016 Beginning Statement of operations Other Ending Deferred tax liabilities Derivative instruments ￦ (19,155 ) ￦ (33,569 ) ￦ 3,536 ￦ (49,188 ) Available-for-sale (29,430 ) (10 ) (2,262 ) (31,702 ) Investment in subsidiaries, associates and joint ventures (50,235 ) (666 ) 155 (50,746 ) Depreciation (53,872 ) 14,374 — (39,498 ) Advanced depreciation provision (231,692 ) 6,005 — (225,687 ) Deposits for severance benefits (251,924 ) (55,806 ) — (307,730 ) Accrued income (1,808 ) (216 ) — (2,024 ) Reserve for technology and human resource development (1,216 ) 469 — (747 ) Others (135,802 ) 16,436 — (119,366 ) (775,134 ) (52,983 ) 1,429 (826,688 ) Deferred tax assets Provisions for impairment on trade receivables 136,743 (26,467 ) — 110,276 Inventory valuation 56 (8 ) — 48 Contribution for construction 19,618 (1,527 ) — 18,091 Accrued expenses 64,117 16,239 — 80,356 Provisions 20,353 (132 ) — 20,221 Property, plant and equipment 239,791 (6,876 ) — 232,915 Retirement benefit obligations 331,980 41,857 (1,345 ) 372,492 Withholding of facilities expenses 7,360 (450 ) — 6,910 Accrued payroll expenses 21,634 4,281 — 25,915 Deduction of installment receivables 10,513 3,374 — 13,887 Assets retirement obligation 16,974 1,112 — 18,086 Gain or loss foreign currency translation 43,283 24,418 — 67,701 Deferred revenue 43,792 (17,679 ) — 26,113 Real-estate sales 2,980 871 — 3,851 (In millions of Korean won) 2016 Beginning Statement of operations Other Ending Tax credit carryforwards 212,820 (13,221 ) — 199,599 Accumulated deficit 107,485 (107,485 ) — — Others 211,382 (17,426 ) — 193,956 1,490,881 (99,119 ) (1,345 ) 1,390,417 Net balance ￦ 715,747 ￦ (152,102 ) ￦ 84 ￦ 563,729 (In millions of Korean won) 2017 Beginning Statement operations Other Ending Deferred tax liabilities Derivative instruments ￦ (49,188 ) ￦ 49,188 ￦ — ￦ — Available-for-sale (31,702 ) (164 ) 1,346 (30,520 ) Investment in subsidiaries, associates and joint ventures (50,746 ) (42,659 ) (3,245 ) (96,650 ) Depreciation (39,498 ) 39,498 — — Advanced depreciation provision (225,687 ) (22,905 ) — (248,592 ) Deposits for severance benefits (307,730 ) (80,126 ) — (387,856 ) Accrued income (2,024 ) (126 ) — (2,150 ) Reserve for technology and human resource development (747 ) 433 — (314 ) Others (119,366 ) 10,617 — (108,749 ) (826,688 ) (46,244 ) (1,899 ) (874,831 ) Deferred tax assets Derivative instruments — 34,572 (9,848 ) 24,724 Provisions for impairment on trade receivables 110,276 11,380 — 121,656 Inventory valuation 48 (48 ) — — Contribution for construction 18,091 180 — 18,271 Accrued expenses 80,356 10,683 — 91,039 Provisions 20,221 3,858 — 24,079 Property, plant and equipment 232,915 (841 ) — 232,074 Retirement benefit obligations 372,492 67,751 26,806 467,049 Withholding of facilities expenses 6,910 472 — 7,382 Accrued payroll expenses 25,915 (10,786 ) — 15,129 Deduction of installment receivables 13,887 (13,887 ) — — Assets retirement obligation 18,086 2,750 — 20,836 Gain or loss foreign currency translation 67,701 (67,558 ) — 143 Deferred revenue 26,113 221 — 26,334 Real-estate sales 3,851 4,847 — 8,698 Tax credit carryforwards 199,599 (48,823 ) — 150,776 Deficit carried over — 2,699 — 2,699 (In millions of Korean won) 2017 Beginning Statement operations Other Ending Others 193,956 47,003 6,743 247,702 1,390,417 44,473 23,701 1,458,591 Net balance ￦ 563,729 ￦ (1,771 ) ￦ 21,802 ￦ 583,760 The tax impacts recognized directly to equity as of December 31, 2015, 2016 and 2017, are as follows: 2015 2016 2017 (In millions of Korean won) Before recognition Tax After Before recognition Tax After Before recognition Tax After Available-for-sale ￦ (47,515 ) ￦ 11,499 ￦ (36,016 ) ￦ 9,347 ￦ (2,262 ) ￦ 7,085 ￦ (5,561 ) ￦ 1,346 ￦ (4,215 ) Hedge instruments valuation gain(loss) 18,406 (4,454 ) 13,952 (14,611 ) 3,536 (11,075 ) 40,694 (9,848 ) 30,846 Remeasurements from net defined benefit liabilities (49,963 ) 12,091 (37,872 ) 5,558 (1,345 ) 4,213 (110,768 ) 26,806 (83,962 ) Shares of gain(loss) of associates and joint ventures (5,297 ) 1,282 (4,015 ) (641 ) 155 (486 ) 13,410 (3,245 ) 10,165 Foreign currency translation adjustment (6,443 ) 1,559 (4,884 ) (7,133 ) 1,726 (5,407 ) (27,865 ) 6,743 (21,122 ) Total ￦ (90,812 ) ￦ 21,977 ￦ (68,835 ) ￦ (7,480 ) ￦ 1,810 ￦ (5,670 ) ￦ (90,090 ) ￦ 21,802 ￦ (68,288 ) Details of income tax expense(benefit) for the years ended December 31, 2015, 2016 and 2017, are calculated as follows: (In millions of Korean won) 2015 2016 2017 Current income tax expense(benefit) ￦ (5,003 ) ￦ 176,212 ￦ 268,885 Impact of change in deferred taxes 232,134 152,102 1,771 Income tax expense ￦ 227,131 ￦ 328,314 ￦ 270,656 The tax on the Group’s profit before tax differs from the theoretical amount that would arise using the weighted average tax rate applicable to profits of the entities as follows: 2015 2016 2017 Profit before income tax expense ￦ 710,741 ￦ 1,123,431 ￦ 816,997 Statutory income tax expense ￦ 171,999 ￦ 271,870 ￦ 197,251 Tax effect Income not taxable for taxation purposes (21,881 ) (28,093 ) (19,268 ) Non-deductible expenses 28,849 21,947 39,746 Tax credit (9,660 ) (13,764 ) (27,211 ) Additional payment of income taxes 997 (4,780 ) 976 Tax effect and adjustment on consolidation Goodwill impairment 23,185 31,847 20,475 Eliminated dividend income form subsidiaries 20,452 40,087 34,305 Changes of out-side tax effect 9,844 (567 ) 17,990 Others 3,346 9,767 6,392 Income tax expense ￦ 227,131 ￦ 328,314 ￦ 270,656

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2017
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Earnings per Share	29. Earnings per Share Basic earnings per share is calculated by dividing the profit from operations attributable to equity holders of the Group by the weighted average number of ordinary shares outstanding during the period, excluding ordinary shares purchased by the Group and held as treasury stock. Basic earnings per share from operations for the years ended December 31, 2015, 2016 and 2017, is calculated as follows: 2015 2016 2017 Profit attributable to ordinary shares (In millions of Korean won) ￦ 546,361 ￦ 708,362 ￦ 461,559 Profit from continuing operations attributable to ordinary shares 404,045 708,362 461,559 Profit from discontinued operations attributable to ordinary shares 142,316 — — Weighted average number of ordinary shares outstanding (In number of shares) 244,854,364 244,892,313 245,017,175 Basic earnings per share (In Korean won) 2,231 2,893 1,884 Basic earnings per share from continuing operations 1,650 2,893 1,884 Basic earnings per share from discontinued operations 581 — — Diluted earnings per share from operations is calculated by adjusting the weighted average number of ordinary shares outstanding to assume conversion of all dilutive potential ordinary shares. The Controlling Company has dilutive potential ordinary shares from convertible preferred stocks, stock options and other share-based payments. Diluted earnings per share from operations for the years ended December 31, 2015, 2016 and 2017 is calculated as follows: 2015 2016 2017 Profit attributable to ordinary shares (In millions of Korean won) ￦ 546,361 ￦ 708,362 ￦ 461,559 Adjusted net income attributable to ordinary shares (In millions of Korean won) (75 ) (67 ) — Diluted profit attributable to ordinary shares (In millions of Korean won) 546,286 708,295 461,559 Diluted profit from continuing operations attributable to ordinary shares 403,970 708,295 461,559 Diluted income from discontinued operations attributable to ordinary shares 142,316 — — Number of dilutive potential ordinary shares outstanding (In number of shares) 1,104 84,245 79,880 Weighted average number of ordinary shares outstanding (In number of shares) 244,855,468 244,976,558 245,097,055 Diluted earnings per share (In Korean won) 2,231 2,891 1,883 Diluted earnings per share from continuing operations 1,650 2,891 1,883 Diluted earnings per share from discontinued operations 581 — —

Dividend

Dividend	12 Months Ended
	Dec. 31, 2017
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Dividend	30. Dividend The dividends paid by the Group in 2017 and 2016 were ￦ ￦ ￦ ￦ ￦ ￦

Cash Generated from Operations

Cash Generated from Operations	12 Months Ended
	Dec. 31, 2017
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Cash Generated from Operations	31. Cash Generated from Operations Cash flows from operating activities for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 1. Profit for the year ￦ 624,685 ￦ 795,117 ￦ 546,341 2. Adjustments to reconcile net income Income tax expense 346,146 328,314 270,656 Interest income (161,123 ) (130,066 ) (108,639 ) Interest expense 445,814 337,219 302,464 Dividends income (11,371 ) (3,926 ) (4,785 ) Depreciation 3,030,821 2,821,779 2,802,531 Amortization of intangible assets 609,185 599,721 635,150 Provision for severance benefits 217,787 217,255 218,966 Impairment losses on trade receivables 161,448 92,711 45,704 Share of net profit or loss of associates and joint ventures (5,562 ) (2,547 ) 15,480 Loss(gain) on disposal of associates and joint ventures (4,848 ) (1,450 ) 979 Impairment loss of associates and joint ventures — 17,128 3,662 Gain on disposal of subsidiaries (256,230 ) — — Loss on disposal of property, plant and equipment and investment in properties 129,466 74,913 150,293 Loss on disposal of intangible assets 33,978 7,703 4,271 Loss on impairment of intangible assets 292,345 135,264 116,095 Loss on foreign currency translation 164,374 109,784 (213,341 ) Loss(gain) on valuation of derivatives (306,538 ) (117,181 ) 268,094 Impairment losses on available-for-sale 1,805 966 9 Gain on disposal of available-for-sale (131,041 ) (22,695 ) (89,598 ) Others 24,140 64,863 (251,193 ) 3. Changes in operating assets and liabilities Decrease(increase) in trade receivables 112,674 252,196 (303,340 ) Increase in other receivables (21,749 ) (770,893 ) (346,013 ) Decrease(increase) in other current assets (19,701 ) 48,549 11,792 Increase in other non-current (137,532 ) (51,765 ) (43,790 ) Decrease(increase) in inventories (270,343 ) 167,873 (205,403 ) Increase(decrease) in trade payables 81,295 (114,838 ) 162,110 Increase(decrease) in other payables (48,680 ) 705,807 214,689 Increase(decrease) in other current liabilities (9,452 ) 37,798 288,553 Increase in other non-current 119,836 30,762 174,618 Decrease in provisions (8,902 ) (12,583 ) (12,574 ) Decrease in deferred revenue (82,582 ) (69,179 ) (13,086 ) Increase in plan assets (223,194 ) (224,244 ) (203,420 ) Payment of severance benefits (117,691 ) (121,835 ) (118,391 ) 4. Cash generated from operations (1+2+3) ￦ 4,579,260 ￦ 5,202,520 4,318,884 The Group made agreements with securitization specialty companies and disposed of its trade receivables related to handset sales (Note 19). Cash flows from the disposals are presented in cash generated from operations. Significant transactions not affecting cash flows for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Reclassification of the current portion of debentures ￦ 1,551,300 ￦ 1,617,175 ￦ 1,416,066 Reclassification of construction-in-progress 2,373,023 2,212,324 2,686,591 Reclassification of accounts payable from property, plant and equipment 78,663 91,407 225,601 Reclassification of accounts payable from intangible assets (170,870 ) 668,564 (227,108 ) Reclassification of payable from defined benefit liability 1,675 5,746 36,209 Reclassification of payable from plan assets 13,717 (9,731 ) 43,035

Changes in Liabilities Arising

Changes in Liabilities Arising from Financing Activities	12 Months Ended
	Dec. 31, 2017
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Changes in Liabilities Arising from Financing Activities	32. Changes in Liabilities Arising from Financing Activities Changes in liabilities arising from financial activities for the periods ended December 31, 2017, are as follows: (in millions of Korean 2017 Beginning Cash flows Non-cash Ending Newly Exchange Fair value Other Borrowing ￦ 8,120,791 ￦ (1,163,917 ) ￦ — ￦ (221,495 ) ￦ — ￦ (51,717 ) ￦ 6,683,662 Financial lease liabilities 180,714 (71,735 ) 68,938 — — (1,039 ) 176,878 Derivative assets 227,318 (71,370 ) — (76,552 ) 2,687 (74,694 ) 7,389 Derivative liabilities 16,901 — — 130,674 (28,015 ) (20,740 ) 98,820 Total ￦ 8,545,724 ￦ (1,307,022 ) ￦ 68,938 ￦ (167,373 ) ￦ (25,328 ) ￦ (148,190 ) ￦ 6,966,749

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
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Segment Information	33. Segment Information The Group’s operating segments are as follows: Details Business service Marketing/Customer Mobile/fixed line telecommunication service and convergence business Finance Credit card business Satellite TV Satellite broadcasting business All other segments Information technology business, security business, global business and other businesses operated by subsidiaries Details of each segment for the years ended December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) Operating revenues Operating income(loss) Depreciation and Amortization Marketing/Customer ￦ 16,130,454 ￦ 816,679 ￦ 2,897,876 Finance 3,512,721 281,477 25,466 Satellite TV 668,521 97,701 95,951 All other segments 6,115,520 (99,601 ) 314,691 26,427,216 1,096,256 3,333,984 Elimination (3,727,360 ) (19,188 ) 4,614 Consolidated amount ￦ 22,699,856 ￦ 1,077,068 ￦ 3,338,598 2016 (In millions of Korean won) Operating revenues Operating income(loss) Depreciation and Amortization Marketing/Customer ￦ 16,144,415 ￦ 1,050,053 ￦ 2,870,161 Finance 3,577,549 208,566 28,868 Satellite TV 668,945 79,987 98,895 All other segments 6,308,203 40,047 339,429 26,699,112 1,378,653 3,337,353 Elimination (3,578,234 ) (38,873 ) 7,913 Consolidated amount ￦ 23,120,878 ￦ 1,339,780 ￦ 3,345,266 2017 (In millions of Korean won) Operating revenues Operating income Depreciation and Amortization Marketing/Customer ￦ 16,242,552 ￦ 1,018,593 ￦ 2,895,930 Finance 3,637,917 205,678 28,827 Satellite TV 685,822 75,373 99,216 All other segments 6,651,552 (187,090 ) 332,153 27,217,843 1,112,554 3,356,126 Elimination (3,670,914 ) (43,462 ) 8,376 Consolidated amount ￦ 23,546,929 ￦ 1,069,092 ￦ 3,364,502 Operating revenues for the year ended December 31, 2015, 2016 and 2017 and non-current (In millions of Korean won) Operating revenues Non-current 1 Location 2015 2016 2017 2016.12.31 2017.12.31 Domestic ￦ ￦ ￦ ￦ ￦ Overseas 71,078 94,623 65,226 174,648 137,914 Total ￦ ￦ ￦ ￦ ￦ 1 Non-current

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
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Related Party Transactions	34. Related Party Transactions The list of related party of the Group as of December 31, 2017, is as follows: Relationship Name of Entry Associates and joint ventures Korea Information & Technology Investment Fund, K- CR-REITs KT-SB KT-CKP K-REALTY CR-REIT ISU-kth KT-DSC start-up Gyeonggi-KT K-REALTY KT-IBKC Gyeonggi-KT Outstanding balances of receivables and payables in relations to transactions with related parties as of December 31, 2016 and 2017, are as follows: 2016 Receivables Payables (In millions of Korean won) Trade Loans Other Trade Other payables Associates and joint ventures KT Wibro Infra Co., Ltd. ￦ — ￦ — ￦ — ￦ — ￦ 43,394 K-Realty CR-REITs 882 — 33,110 — — MOS GS Co., Ltd. 9 — 1 — 1,494 MOS Daegu Co., Ltd. 1 — — — 1,082 MOS Chungcheong Co., Ltd. 6 — 1 — 2,065 MOS Gangnam Co., Ltd. 6 — 1 — 1,129 MOS GB Co., Ltd. 19 — 5 — 2,167 MOS BS Co., Ltd. 34 — 1 — 1,114 MOS Honam Co., Ltd. 2 — — — 1,289 Others 481 — 179 3 1,266 Total ￦ 1,440 ￦ — ￦ 33,298 ￦ 3 ￦ 55,000 2017 Receivables Payables (In millions of Korean won) Trade Loans Other Trade Other payables Associates and joint ventures K-Realty CR-REITs ￦ 778 ￦ — ￦ 33,800 ￦ — ￦ — MOS GS Co., Ltd. 17 — — — 392 MOS Daegu Co., Ltd. 1 — — — 1,388 MOS Chungcheong Co., Ltd. 1 — 290 — 1,827 MOS Gangnam Co., Ltd. 6 — 1 — 287 MOS GB Co., Ltd. 17 — 1 — 778 MOS BS Co., Ltd. 34 — 1 — 46 MOS Honam Co., Ltd. 2 — 1 — 384 K Bank, Inc. 1,338 — 7,994 — 296 NgeneBio 1 2,510 — — 3 Others 54 — 1,281 — 2,135 Total ￦ 2,249 ￦ 2,510 ￦ 43,369 ￦ — ￦ 7,536 Significant transactions with related parties for the years ended December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) Sales Purchases 2 Associates and joint ventures KT Service Bukbu 1 ￦ 2,143 ￦ 28,550 Information Technology Solution Nambu Corporation 1 2,707 24,025 Information Technology Solution Seobu Corporation 1 2,324 20,031 Information Technology Solution Busan Corporation 1 1,496 14,049 KT Service Nambu 1 1,972 21,133 Information Technology Solution Honam Corporation 1 2,050 29,538 Information Technology Solution Daegu Corporation 1 1,256 18,272 KT Wibro Infra Co., Ltd. 11 814 Smart Channel Co., Ltd. 6,545 4,722 K- CR-REITs 2,133 38,167 MOS GS Co., Ltd. 752 17,474 MOS Daegu Co., Ltd. 357 12,227 MOS Chungcheong Co., Ltd. 310 12,735 MOS Gangnam Co., Ltd. 454 15,829 MOS GB Co., Ltd. 964 21,582 MOS BS Co., Ltd. 453 15,482 MOS Honam Co., Ltd. 470 17,004 Others 4,394 13,510 Total 3 ￦ 30,791 ￦ 325,144 1 The transactions for the year ended December 31, 2015, after KT Service Bukbu Co., Ltd. and KT Service Nambu Co., Ltd. were merged and included in the consolidation scope. 2 The amount includes acquisition of property, plant and equipment, and others. 3 Operating income amounting to ￦ 2016 (In millions of Korean won) Sales Purchases 2 Associates and joint ventures KT Wibro Infra Co., Ltd. ￦ 11 ￦ 391 Smart Channel Co., Ltd. 1 766 — K- CR-REITs 1,989 37,469 MOS GS Co., Ltd. 663 17,361 MOS Daegu Co., Ltd. 291 12,220 MOS Chungcheong Co., Ltd. 408 13,469 MOS Gangnam Co., Ltd. 412 15,797 MOS GB Co., Ltd. 891 21,802 MOS BS Co., Ltd. 441 15,346 MOS Honam Co., Ltd. 418 14,389 Others 1,719 29,422 Total ￦ 8,009 ￦ 177,666 1 The transactions for the year ended December 31, 2016, before Smart Channel Co., Ltd. was included in the consolidation scope. 2 The amount includes acquisition of property, plant and equipment, and others. 2017 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 2,233 ￦ 35,532 MOS GS Co., Ltd. 704 16,946 MOS Daegu Co., Ltd. 335 8,514 MOS Chungcheong Co., Ltd. 455 15,542 MOS Gangnam Co., Ltd. 484 16,380 MOS GB Co., Ltd. 987 21,651 MOS BS Co., Ltd. 460 15,957 MOS Honam Co., Ltd. 493 14,294 K Bank, Inc. 3 29,939 59 NgeneBio 2 43 — Others 1,149 11,384 Total ￦ 37,282 ￦ 156,259 1 The amount includes acquisition of property, plant and equipment and others. 2 It is the amount after excluded from consolidation during the year. 3 The sales amount consists of providing services of IT system construction to K Bank, Inc. Key management compensation for the years ended December 31, 2015, 2016 and 2017, consists of: (In millions of Korean won) 2015 2016 2017 Salaries and other short-term benefits ￦ 2,455 ￦ 2,629 ￦ 2,879 Post-employment benefits 413 381 311 Stock-based compensation 997 1,237 1,331 Total ￦ 3,865 ￦ 4,247 ￦ 4,521 Fund transactions with related parties for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Equity Dividend Associates and joint ventures KT-DSC start-up ￦ 6,000 ￦ — PT. Mitra Transaksi Indonesia 16,626 — K-REALTY 5,500 — AI RESEARCH INSTITUTE 3,000 — KT-IBKC 3,750 — Gyeonggi-KT 1,000 — FUNDA Co., Ltd. 2,799 — K-Realty CR-REITs — 4,186 Korea Information & Technology Investment Fund — 3,201 Daiwon Broadcasting Co., Ltd. — 85 Others — 82 Total ￦ 38,675 ￦ 7,554 (In millions of Korean won) 2017 Equity Dividend Associates and joint ventures PT. Mitra Transaksi Indonesia ￦ 5,194 ￦ — KT-IBKC 7,500 — CHAMP IT Co.,Ltd. 750 — Korea Electronic Vehicle Charging Service 864 — Gyeonggi-KT 1,000 — K-REALTY — 5,392 K Bank, Inc. 26,543 — Korea Information & Technology Investment Fund — 739 MOS GS Co., Ltd. — 12 MOS Daegu Co., Ltd. — 12 MOS Chungcheong Co., Ltd. — 12 MOS Gangnam Co., Ltd. — 10 MOS GB Co., Ltd. — 15 MOS BS Co., Ltd. — 10 MOS Honam Co., Ltd. — 10 Total ￦ 41,851 ￦ 6,212

Financial Risk Management

Financial Risk Management	12 Months Ended
	Dec. 31, 2017
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Financial Risk Management	35. Financial Risk Management (1) Financial Risk Factors The Group’s activities expose it to a variety of financial risks: market risk (including currency risk, fair value interest rate risk, cash flow interest rate risk and price risk), credit risk and liquidity risk. The Group’s overall risk management program focuses on the unpredictability of financial markets and seeks to minimize potential adverse effects on the Group’s financial performance. The Group uses derivative financial instruments to hedge certain risk exposures. The Group’s financial policy is set up in the long-term perspective and annually reported to the Board of Directors. The financial risk management is carried out by the Value Management Office, which identifies, evaluates and hedges financial risks. The treasury department in the Value Management Office considers various finance market conditions to estimate the effect from the market changes. 1) Market risk The Group’s market risk management focuses on controlling the extent of exposure to the risk in order to minimize revenue volatility. Market risk is a risk that decreases value or profit of the Group’s portfolio due to changes in market interest rate, foreign exchange rate and other factors. (i) Sensitivity analysis Sensitivity analysis is performed for each type of market risk to which the Group is exposed. Reasonably possible changes in the relevant risk variable such as prevailing market interest rates, currency rates, equity prices or commodity prices are estimated and if the rate of change in the underlying risk variable is stable, the Group does not alter the chosen reasonably possible change in the risk variable. The reasonably possible change does not include remote or ‘worst case’ scenarios or ‘stress tests’. (ii) Foreign exchange risk The Group is exposed to foreign exchange risk arising from operating, investing and financing activities. Foreign exchange risk is managed within the range of the possible effect on the Group’s cash flows. Foreign exchange risk unaffecting the Group’s cash flows is not hedged but can be hedged at a particular situation. As of December 31, 2015, 2016 and 2017, if the foreign exchange rate had strengthened/weakened by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of Income before tax Shareholders’ equity 2015.12.31 10 % ￦ (52,157 ) ￦ (45,632 ) -10 % 52,157 45,632 2016.12.31 10 % (28,134 ) (23,817 ) -10 % 28,134 23,817 2017.12.31 10 % (10,132 ) (7,273 ) -10 % 10,132 7,273 The above analysis is a simple sensitivity analysis which assumes that all the variables other than foreign exchange rates are held constant. Therefore, the analysis does not reflect any correlation between foreign exchange rates and other variables, nor the management’s decision to decrease the risk. Details of financial assets and liabilities in foreign currencies as of December 31, 2015, 2016 and 2017, are as follows: 2015 2016 2017 (In thousands) Financial Financial liabilities Financial Financial Financial Financial USD 183,254 2,351,003 210,474 2,536,090 236,476 1,908,831 SDR 1 444 849 311 737 306 738 JPY 73,716 40,279,411 80,555 21,802,051 28,267 21,801,443 GBP 8 888 1 151 — 74 EUR 29 29 40 2,571 186 3,625 DZD 2 — — 471 — 47 — CNY 15,562 107 15,262 381 46,555 10 UZS 3 — — 39,531 — 136,787 — RWF 4 — — 1,203 — 3,346 — IDR 5 — — 15,646,011 53,142,167 14,886,393 710,162 MMK 6 — — 2,750 — 84 — TZS 7 — — 29,987 — 317,348 — BWP 8 — — 15 — 42 — HKD 9 — 254 — — — BDT 9 6 — 69,473 — 38,074 — PLN 10 207,273 — 106,025 — 338 — VND 11 270,000 — 515,412 — 311,649 — CHF 12 — — — — — 12 1 Special Drawing Rights. 2 Algeria Dinar. 3 Uzbekistan Sum. 4 Rwanda Franc. 5 Indonesia Rupiah. 6 Myanmar Kyat. 7 Tanzanian Shilling. 8 Botswana Pula. 9 Bangladesh Taka. 10 Polish Zloty. 11 Vietnam Dong. 12 Confoederatio Helvetia Franc. (iii) Price risk As of December 31, 2015, 2016 and 2017, the Group is exposed to equity securities price risk because the securities held by the Group are traded in active markets. If the market prices had increased/decreased by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of price Income before tax Equity 2015.12.31 10% ￦ — ￦ 3,469 -10% — (3,469 ) 2016.12.31 10% ￦ — ￦ 539 -10% — (539 ) 2017.12.31 10% ￦ — ￦ 686 -10% — (686 ) The above analysis is based on the assumption that the equity index had increased/decreased by 10% with all other variables held constant and all the Group’s marketable equity instruments had moved according to the historical correlation with the index. (iv) Cash flow and fair value interest rate risk The Group’s interest rate risk arises from liabilities in foreign currency such as foreign currency debentures. Debentures in foreign currency issued at variable rates expose the Group to cash flow interest rate risk which is partially offset by swap transactions. Debentures and borrowings issued at fixed rates expose the Group to fair value interest rate risk. The Group sets the policy and operates to minimize the uncertainty of the changes in interest rates and financial costs. As of December 31, 2015, 2016 and 2017, if the market interest rate had increased/decreased by 100bp with other variables held constant, the effects on profit before income tax and shareholders’ equity would be as follows: (In millions of Korean won) Fluctuation of interest rate Income before tax Shareholders’ 2015.12.31 + 100 bp ￦ (3,601 ) ￦ (245 ) - 100 bp 3,615 (5,764 ) 2016.12.31 + 100 bp ￦ (3,456 ) ￦ (1,673 ) - 100 bp 3,445 (5,025 ) 2017.12.31 + 100 bp ￦ 1,942 ￦ 4,868 - 100 bp (1,954 ) (5,198 ) The above analysis is a simple sensitivity analysis which assumes that all the variables other than market interest rates are held constant. Therefore, the analysis does not reflect any correlation between market interest rates and other variables, nor the management’s decision to decrease the risk. 2) Credit risk Credit risk is managed on the Group basis with the purpose of minimizing financial loss. Credit risk arises from the normal transactions and investing activities, where clients or other party fails to discharge an obligation on contract conditions. To manage credit risk, the Group considers the counterparty’s credit based on the counterparty’s financial conditions, default history and other important factors. Credit risk arises from cash and cash equivalents, derivative financial instruments and deposits with banks and financial institutions, as well as outstanding receivables. To minimize such risk, only the financial institutions with strong credit ratings are accepted. As of December 31, 2016 and 2017, maximum exposure to credit risk is as follows. (In millions of Korean won) 2016 2017 Cash equivalents(except cash on hand) ￦ 2,875,383 ￦ 1,926,620 Trade and other receivables 6,036,363 6,643,115 Other financial assets Financial assets at fair value through profit or loss 6,277 5,813 Derivative used for hedging 227,318 7,389 Time deposits and others 716,769 1,333,317 Available-for-sale 26,684 9,899 Held-to-maturity 30,143 151 Financial guarantee contracts 1 56,373 143,969 Total ￦ 9,975,310 ￦ 10,070,273 1 Total amounts guaranteed by the Group according to the guarantee contracts. 3) Liquidity risk The Group manages its liquidity risk by liquidity strategy and plans. The Group considers the maturity of financial assets and financial liabilities and the estimated cash flows from operations. The table below analyzes the Group’s liabilities (including interest expenses) into relevant maturity groups based on the remaining period at the date of the end of each reporting period to the contractual maturity date. These amounts are contractual undiscounted cash flows. 2016.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Trade and other payables ￦ 7,682,604 ￦ 1,121,452 ￦ 217,411 ￦ 9,021,467 Borrowings(including debentures) 2,034,524 4,834,151 2,458,749 9,327,424 Other non-derivative 233 3,272 22,917 26,422 Financial guarantee contracts 1 56,373 — — 56,373 Total ￦ 9,773,734 ￦ 5,958,875 ￦ 2,699,077 ￦ 18,431,686 2017.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Trade and other payables ￦ 7,880,906 ￦ 1,219,835 ￦ 161,497 ￦ 9,262,238 Borrowings(including debentures) 1,623,996 3,666,726 2,317,209 7,607,931 Other non-derivative 4,117 8,452 — 12,569 Financial guarantee contracts 1 26,738 — — 26,738 Total ￦ 9,535,757 ￦ 4,895,013 ￦ 2,478,706 ￦ 16,909,476 1 Total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed. Cash outflow and inflow of derivatives settled gross or net are undiscounted contractual cash flow and can differ from the amount in the financial statements. 2015.12.31 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 335,970 ￦ 2,138,379 ￦ 38,184 ￦ 2,512,533 Inflow 276,066 2,284,219 46,194 2,606,479 2016.12.31 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 1,174,147 ￦ 1,176,715 ￦ 536,005 ￦ 2,886,867 Inflow 1,302,112 1,306,199 588,559 3,196,870 2017.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Outflow ￦ 638,171 ￦ 546,791 ￦ 526,633 ￦ 1,711,595 Inflow 608,270 568,976 509,558 1,686,804 (2) Management of Capital Management The Group’s objectives when managing capital are to safeguard the Group’s ability to continue as a going concern in order to provide returns for shareholders and benefits for other shareholders and to maintain an optimal capital structure to reduce the cost of capital. The Group’s capital structure consists of liabilities including borrowings, cash and cash equivalents, and shareholders’ equity. The treasury department monitors the Group’s capital structure and considers cost of capital and risks related each capital component. The debt-to-equity (In millions of Korean won) 2016 2017 Total liabilities ￦ 17,881,580 ￦ 16,696,309 Total equity 12,782,718 13,049,130 Debt-to-equity 140 % 128 % The Group manages capital on the basis of the gearing ratio. This ratio is calculated as net debt divided by total capital. Net debt is calculated as total borrowings less cash and cash equivalents. Total capital is calculated as ‘equity’ in the statement of financial position plus net debt. The gearing ratios as of December 31, 2016 and 2017, are as follows: (In millions of Korean won, %) 2016 2017 Total borrowings ￦ 8,301,505 ￦ 6,860,539 Less: cash and cash equivalents (2,900,311 ) (1,928,182 ) Net debt 5,401,194 4,932,357 Total equity 12,782,718 13,049,130 Total capital 18,183,912 17,981,487 Gearing ratio 30 % 27 % (3) Offsetting Financial Assets and Financial Liabilities Details of the Group’s recognized financial assets subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) 2016 Gross Gross Net amounts position Amounts not offset Net Financial Cash Derivative assets for hedging purpose 1 ￦ 35,334 ￦ — ￦ 35,334 ￦ (5,707 ) ￦ — ￦ 29,627 Trade receivables 2 95,865 — 95,865 (91,662 ) — 4,203 ￦ 131,199 ￦ — ￦ 131,199 ￦ (97,369 ) ￦ — ￦ 33,830 (In millions of Korean won) 2017 Gross Gross Net amounts position Amounts not offset Net Financial Cash Derivative assets for hedging purpose 1 ￦ 3,284 ￦ — ￦ 3,284 ￦ (3,284 ) ￦ — ￦ — Trade receivables 2 85,755 (5,010 ) 80,745 (73,109 ) — 7,636 Other financial assets 8,680 (436 ) 8,244 (5,307 ) — 2,937 ￦ 97,719 ￦ (5,446 ) ￦ 92,273 ￦ (81,700 ) ￦ — ￦ 10,573 1 The amount applied with master netting arrangements under the standard contract of International Swap and Derivatives Association (ISDA). 2 The amount applied with netting arrangements under the reference offer of the telecommunication facility interconnection and sharing data among telecommunications companies. The Group’s recognized financial liabilities subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) 2016 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Derivative liabilities for hedging purpose 1 ￦ 20,627 ￦ — ￦ 20,627 ￦ (20,627 ) ￦ — ￦ — Trade payables 2 90,435 — 90,435 (86,184 ) — 4,251 Other payables 2 48 (4 ) 44 — — 44 ￦ 111,110 ￦ (4 ) ￦ 111,106 ￦ (106,811 ) ￦ — ￦ 4,295 (In millions of Korean won) 2017 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Derivative liabilities for hedging purpose 1 ￦ 26,135 ￦ — ￦ 26,135 ￦ (3,284 ) ￦ — ￦ 22,851 Trade payables 2 80,829 (5,217 ) 75,612 (73,109 ) — 2,503 Other financial liabilities 5,549 (229 ) 5,320 (5,307 ) — 13 ￦ 112,513 ￦ (5,446 ) ￦ 107,067 ￦ (81,700 ) ￦ — ￦ 25,367 1 The amount applied with master netting arrangements under the standard contract of International Swap and Derivatives Association (ISDA). 2 The amount applied with netting arrangements under the reference offer of the telecommunication facility interconnection and sharing data among telecommunications companies.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Fair Value	36. Fair Value 36.1 Fair Value of Financial Instruments by Category Carrying amount and fair value of financial instruments by category as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Carrying Fair value Carrying Fair value Financial assets Cash and cash equivalents 1 ￦ ￦ ￦ ￦ Trade and other receivables 1 6,036,363 — 6,643,115 — Other financial assets Financial instruments at fair value through profit or loss 6,277 6,277 5,813 5,813 Derivative financial instruments for hedging purpose 227,318 227,318 7,389 7,389 Time deposits and others 1 716,769 — 1,333,317 — Held-to-maturity 30,143 30,143 151 151 Available-for-sale 2 299,001 299,001 319,402 319,402 ￦ ￦ ￦ ￦ Financial liabilities Trade and other liabilities 1 ￦ ￦ ￦ ￦ Borrowings 8,120,791 8,184,195 6,683,662 6,738,326 Other financial liabilities Financial instruments at fair value through profit or loss 1,973 1,973 5,051 5,051 Derivative financial instruments for hedging purpose 14,928 14,928 93,770 93,770 Other 1 91,763 — 87,670 — ￦ ￦ ￦ ￦ 1 The Group did not conduct fair value estimation since the book amount is a reasonable approximation of the fair value. 2 Equity instruments that do not have a quoted price in an active market are measured at cost because their fair value cannot be measured reliably and excluded from the fair value disclosures. 36.2 Financial Instruments Measured at Cost Available-for-sale (In millions of Korean won) 2016 2017 K-Bank ￦ 36,500 ￦ — IBK-AUCTUS Green Growth Private Equity Fund 9,506 8,518 WALDEN No.6 Fund 4,710 4,670 TRANSLINK No.2 Fund 9,395 9,395 Storm IV Fund 7,550 8,453 CBC II Fund 8,601 7,298 Others 29,511 23,217 ￦ 105,773 ￦ 61,551 The range of cash flow estimates is significant and the probabilities of the various estimates cannot be reasonably assessed and therefore, these instruments are measured at cost. The Group does not have any plans to dispose of the above-mentioned equities instruments in the near future. These instruments will be measured at fair value when the Group can develop a reliable estimate of the fair value. 36.3 Fair Value Hierarchy Assets measured at fair value or for which the fair value is disclosed are categorized within the fair value hierarchy, and the defined levels are as follows: • Quoted prices (unadjusted) in active markets for identical assets or liabilities (Level 1). • Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly (that is, prices) or indirectly (that is, derived from prices) (Level 2). • Inputs for the asset or liability that are not based on observable market data (that is, unobservable inputs) (Level 3). Fair value hierarchy classifications of the financial assets and financial liabilities that are measured at fair value or its fair value is disclosed as of December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Level 1 Level 2 Level 3 Total Recurring fair value measurements Other financial assets Financial assets at fair value through profit or loss ￦ — ￦ — ￦ 6,277 ￦ 6,277 Derivative financial assets for hedging purpose — 227,318 — 227,318 Available-for-sale 5,387 5,725 287,889 299,001 5,387 233,043 294,166 532,596 Disclosed fair value Associates and joint ventures 3,940 — — 3,940 Investment properties 1 — — 1,962,779 1,962,779 3,940 — 1,962,779 1,966,719 ￦ 9,327 ￦ 233,043 ￦ 2,256,945 ￦ 2,499,315 Recurring fair value measurements Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ — ￦ 1,973 ￦ 1,973 Derivative financial liabilities for hedging purpose — 14,928 — 14,928 — 14,928 1,973 16,901 Disclosed fair value Borrowings — — 8,184,195 8,184,195 — — 8,184,195 8,184,195 ￦ — ￦ 14,928 ￦ 8,186,168 ￦ 8,201,096 2017 (In millions of Korean won) Level 1 Level 2 Level 3 Total Recurring fair value measurements Other financial assets Financial assets at fair value through profit or loss ￦ — ￦ — ￦ 5,813 ￦ 5,813 Derivative financial assets for hedging purpose — 7,389 — 7,389 Available-for-sale 6,859 5,466 307,077 319,402 6,859 12,855 312,890 332,604 Disclosed fair value Investment properties 1 — — 1,755,600 1,755,600 — — 1,755,600 1,755,600 ￦ 6,859 ￦ 12,855 ￦ 2,068,490 ￦ 2,088,204 Recurring fair value measurements Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ — ￦ 5,051 ￦ 5,051 Derivative financial liabilities for hedging purpose — 76,045 17,725 93,770 — 76,045 22,776 98,821 Disclosed fair value Borrowings — — 6,738,326 6,738,326 — — 6,738,326 6,738,326 ￦ — ￦ 76,045 ￦ 6,761,102 ￦ 6,837,147 1 The highest and best use of a non-financial 36.4 Transfers Between Fair Value Hierarchy Levels of Recurring Fair Value Measurements (a) Details of transfers between Level 1 and Level 2 of the fair value hierarchy for the recurring fair value measurements are as follows: There are no transfers between Level 1 and Level 2 of the fair value hierarchy for the recurring fair value measurements. (b) Details of changes in Level 3 of the fair value hierarchy for the recurring fair value measurements are as follows: 2016 (In millions of Korean won) Financial assets profit or loss Available-for-sale Other derivative financial Beginning balance ￦ 18 ￦ 267,337 ￦ 2,006 Reclassification — 5,723 — Amount recognized in other comprehensive income — 15,099 — Purchases 13,461 1,561 — Amount recognized in profit or loss (7,184 ) (426 ) (33 ) Sales (18 ) (1,405 ) — Ending balance ￦ 6,277 ￦ 287,889 ￦ 1,973 2017 (In millions of Korean won) Financial assets at Available-for-sale Other derivative Derivative financial Beginning balance ￦ 6,277 ￦ 287,889 ￦ 1,973 ￦ — Reclassification — (277 ) — — Amount recognized in other comprehensive income — 58,450 — (1,909 ) Purchases — 85,287 — — Amount recognized in profit or loss (464 ) (113 ) 3,078 19,634 Sales — (124,159 ) — — Ending balance ￦ 5,813 ￦ 307,077 ￦ 5,051 ￦ 17,725 36.5 Valuation Technique and the Inputs Valuation techniques and inputs used in the recurring, non-recurring 2016 (In millions of Korean won) Fair value Level Valuation techniques Assets Recurring fair value measurements Other financial assets Derivative financial assets for hedging purpose ￦ 227,318 2 Discounted cash flow model Available-for-sale 293,614 2,3 Discounted cash flow model Others 6,277 3 Discounted cash flow model Disclosed fair value Investment properties 1,962,779 3 Discounted cash flow model Liabilities Recurring fair value measurements Other financial liabilities Derivative financial liabilities for hedging purpose 14,928 2 Discounted cash flow model Other derivative financial liabilities 1,973 3 Discounted cash flow model Comparable Company Disclosed fair value Borrowings 8,184,195 3 Discounted cash flow model 2017 (In millions of Korean won) Fair value Level Valuation techniques Assets Recurring fair value measurements Other financial assets Derivative financial assets for hedging purpose ￦ 7,389 2 Discounted cash flow model Available-for-sale 312,543 2,3 Discounted cash flow model Others 5,813 3 Discounted cash flow model Disclosed fair value Investment properties 1,755,600 3 Discounted cash flow model Liabilities Recurring fair value measurements Other financial liabilities Derivative financial liabilities for hedging purpose 93,770 2,3 Hull-White Model, Discounted cash flow model Other derivative financial liabilities 5,051 3 Discounted cash flow model Comparable Company Analysis Disclosed fair value Borrowings 6,738,326 3 Discounted cash flow model 36.6 Valuation Processes for Fair Value Measurements Categorized Within Level 3 The Group uses external experts that perform the fair value measurements required for financial reporting purposes. External experts report directly to the chief financial officer (CFO), and discusses valuation processes and results with the CFO in line with the Group’s reporting dates. 36.7 Gains and losses on valuation at the transaction date In the case that the Group values derivative financial instruments using inputs not based on observable market data, and the fair value calculated by the said valuation technique differs from the transaction price, then the fair value of the financial instruments is recognized as the transaction price. The difference between the fair value at initial recognition and the transaction price is deferred and amortized using a straight-line method by maturity of the financial instruments. However, in the case that inputs of the valuation techniques become observable in markets, the remaining deferred difference is immediately recognized in full in profit for the year. In relation to this, details and changes of the total deferred difference for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other derivative Other derivative Other derivative Other derivative Beginning balance ￦ 11,293 ￦ — ￦ 8,470 ￦ — New transactions — — — 7,126 Disposal (2,823 ) — (2,823 ) (594 ) Ending balance ￦ 8,470 ￦ — ￦ 5,647 ￦ 6,532

Interests in Unconsolidated Str

Interests in Unconsolidated Structured Entities	12 Months Ended
	Dec. 31, 2017
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Interests in Unconsolidated Structured Entities	37. Interests in Unconsolidated Structured Entities Details of information about its interests in unconsolidated structured entities, which the Group does not have control over, including the nature, purpose and activities of the structured entity and how the structured entity is financed, are as follows: Classes of entities Nature, purpose, activities and others Real estate finance A structured entity incorporated for the purpose of real estate development is provided with funds by investors’ investments in equity and borrowings from financial institutions (including long-term and short-term loans and issuance of ABCP due in three months), and based on these, the structured entity implements activities such as real estate acquisition, development and mortgage loans. The structured entity repays loan principals with funds incurred from instalment house sales after the completion of real estate development or with collection of the principal of mortgage loan. The remaining shares are distributed to investors. As of December 31, 2017, this entity is engaged in real estate finance structured entity, and generates revenues by receiving dividends from direct investments in or receiving interests on loans to the structured entity. Financial institutions, including the Entity, are provided with guarantees including joint guarantees or real estate collateral from investors and others. Remarks Nature, purpose, activities and others Consequently, the entity is a priority over other parties in the preservation of claim. However, when the credit rating of investors and others decreases or when the value of real estate decreases, the entity may be obliged to cover losses. PEF and investment funds Minority investors including managing members contribute to PEF and investment funds incorporated for the purpose of providing funds to the small, medium, or venture entities, and the managing member implements activities such as investments in equity or loans based on the contributions. As of December 31, 2017, the entity is engaged in PEF and investment funds structured entity, and after contributing to PEF and investment funds, the entity receives dividends for operating revenues from these contributions. The entity is provided with underlying assets of PEF and investment funds as collateral. However, when the value of the underlying assets decreases, the entity may be obliged to cover losses. M&A finance A structured entity incorporated for the purpose of supporting a certain group’s financial structure improvement or acquiring equity or convertible bonds is provided with funds by investors’ investments in equity and long-term or short-term borrowings from financial institutions, and based on these, the structured entity acquires shares held by the entity, which has plans to improve its financial structure, or to dispose convertible bonds and others. The structured entity repays loan principals with funds incurred from disposals of holding shares after a certain period. The remaining shares are distributed to investors. As of December 31, 2017, the entity is engaged in M&A finance structured entity, and receives interests. Financial institutions are provided with guarantees including joint guarantees or shares subject to M&A from investors and others. Consequently, the entity is a priority over other parties in the preservation of claim. However, when the credit rating of investors and others decreases or when the value of shares provided as collateral decreases, the Group may be obliged to cover losses. Asset securitization The Group transfers accounts receivable for handset sales to its Special Purpose Company (“SPC”) for asset securitization. SPC issues the asset-backed securities with accounts receivable for handset sales as an underlying asset, and makes payment for the underlying asset acquired. Other There are other structured entity types, which the entity is engaged in, such as shipping finance, SPAC and others. Interest income is realized from the entity’s loans to the relevant structured entity. When the credit rating of the shipping group decreases, or the value of vessels decreases, the entity may be obliged to cover losses. When SPAC is listed or merged after the entity invests in shares or convertible bonds issued by the relevant structured entity, revenues are realized from disposal of the shares of the convertible bonds. However, the entity may be obliged to cover losses when SPAC is liquidated if the SPAC is not listed or merged. Details of scale of unconsolidated structured entities and nature of the risks associated with an entity’s interests in unconsolidated structured entities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Real Estate Finance PEF &Investment Asset-backed Total Total assets of Unconsolidated Structured Entities ￦ 1,075,471 ￦ 3,759,246 ￦ 2,841,886 ￦ 7,676,603 Assets recognized in statement of financial position Other financial assets ￦ 21,932 ￦ 60,782 ￦ — ￦ 82,714 Joint ventures and Associates 10,086 165,638 — 175,724 Total ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 Maximum loss exposure1 Investment Assets ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 Total ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 1 Maximum exposure to loss includes the investments recognized in the Group’s financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others. (In millions of Korean won) 2017 Real Estate Finance PEF &Investment Asset-backed Total Total assets of Unconsolidated Structured Entities ￦ 1,426,620 ￦ 3,779,377 ￦ 2,619,445 ￦ 7,825,442 Assets recognized in statement of financial position Other financial assets ￦ 21,800 ￦ 52,666 — ￦ 74,466 Joint ventures and Associates 10,168 164,030 — 174,198 Total ￦ 31,968 ￦ 216,696 ￦ — ￦ 248,664 Maximum loss exposure1 Investment Assets ￦ 31,968 ￦ 216,696 — ￦ 248,664 Total ￦ 31,968 ￦ 216,696 ￦ — ￦ 248,664 1 Maximum exposure to loss includes the investments recognized in the Group’s financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others.

Information About Non-controlli

Information About Non-controlling Interests	12 Months Ended
	Dec. 31, 2017
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Information About Non-controlling Interests	38. Information About Non-controlling 38.1 Changes in Accumulated Non-controlling Profit or loss allocated to non-controlling non-controlling (In millions of Korean won) 2015 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 297,300 ￦ 27,032 ￦ (8,325 ) ￦ 873 ￦ 316,880 BC Card Co., Ltd. 30.46 % 292,931 62,943 (22,650 ) (10,303 ) 322,921 KT Powertel Co., Ltd. 55.15 % 70,231 (17,880 ) (1,118 ) (307 ) 50,926 KT Hitel Co.,Ltd. 36.30 % 51,136 (608 ) — 161 50,689 KT Telecop Co., Ltd. 13.18 % 104,821 (1,000 ) — (393 ) 103,428 (In millions of Korean won) 2016 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 316,880 ￦ 22,445 ￦ (8,279 ) ￦ (1,370 ) ￦ 329,676 BC Card Co., Ltd. 30.46 % 322,921 47,068 (44,637 ) 3,986 329,338 KT Powertel Co., Ltd. 55.15 % 50,926 112 — 713 51,751 KT Hitel Co.,Ltd. 35.27 % 50,689 1,274 — (165 ) 51,798 KT Telecop Co., Ltd. 13.18 % 103,428 19 — 85 103,532 (In millions of Korean won) 2017 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 329,676 ￦ 9,395 ￦ (9,817 ) ￦ (952 ) ￦ 328,302 BC Card Co., Ltd. 30.46 % 329,338 43,961 (29,490 ) (4,742 ) 339,067 KT Powertel Co., Ltd. 55.15 % 51,751 1,165 — 137 53,053 KT Hitel Co.,Ltd. 32.87 % 51,798 870 — 478 53,146 KT Telecop Co., Ltd. 13.18 % 103,532 381 — (445 ) 103,468 38.2 Summarized Financial Information on Subsidiaries The summarized financial information for each subsidiary with non-controlling Summarized consolidated statements of financial position as of December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 36.30 % 13.18 % Current assets ￦ 279,480 ￦ 2,291,047 ￦ 65,739 ￦ 157,355 ￦ 58,457 Non-current 431,814 672,905 47,776 78,402 210,734 Current liabilities 143,511 1,882,363 16,016 33,656 82,353 Non-current 74,339 63,271 5,166 282 52,613 Equity 493,444 1,018,318 92,333 201,819 134,225 Accumulated non-controlling 316,880 322,921 50,926 50,689 103,428 Operating revenue 668,521 3,504,946 104,527 162,155 302,844 Profit or loss for the year 72,987 218,969 (32,417 ) 7,258 (7,593 ) Total comprehensive income 73,147 188,360 (32,417 ) 6,769 (7,593 ) The profit or loss allocated to non-controlling 27,032 62,943 (17,880 ) (608 ) (1,000 ) Cash flows from operating activities 157,762 128,927 (12,016 ) 22,556 36,216 Cash flows from investing activities (92,350 ) 73,118 10,691 (19,949 ) (91,846 ) Cash flows from financing activities before dividend paid to non-controlling (35,984 ) (75,121 ) (2,015 ) — (32,491 ) Dividend paid to non-controlling (8,325 ) (22,650 ) (1,118 ) — — Net (decrease)/increase in cash and cash equivalents 29,428 126,924 (3,340 ) 2,607 (88,121 ) 2016 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel Co., Ltd. KT Hitel Co., Ltd. KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 35.27 % 13.18 % Current assets ￦ 352,980 ￦ 2,945,584 ￦ 69,046 ￦ 158,210 ￦ 63,802 Non-current 424,968 705,480 44,679 90,992 201,751 Current liabilities 151,329 2,530,832 17,910 45,277 53,903 Non-current 80,123 71,571 1,989 1,664 78,441 Equity 546,496 1,048,661 93,826 202,261 133,209 Accumulated non-controlling 329,676 329,338 51,751 51,798 103,532 Operating revenue 668,945 3,567,512 81,390 198,994 315,948 Profit or loss for the year 68,863 163,131 202 4,298 143 Total comprehensive income 68,785 178,744 202 1,399 143 The profit or loss allocated to non-controlling 22,445 47,068 112 1,274 19 Cash flows from operating activities 155,399 92,818 7,271 28,987 60,461 Cash flows from investing activities (210,480 ) (37,313 ) (8,191 ) (33,238 ) (45,243 ) Cash flows from financing activities before dividend paid to non-controlling (16,647 ) (147,306 ) — — — Dividend paid to non-controlling (8,279 ) (44,637 ) — — — Gain or loss foreign currency translation — (178 ) — 3 — Net (decrease)/increase in cash and cash equivalents (71,728 ) (91,801 ) (920 ) (4,251 ) 15,218 2017 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel Co., Ltd. KT Hitel Co., Ltd. KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 32.87 % 13.18 % Current assets ￦ 324,632 ￦ 3,225,262 ￦ 73,527 ￦ 150,368 ￦ 73,023 Non-current 468,261 823,001 41,598 107,872 191,330 Current liabilities 185,995 2,868,669 18,450 49,922 90,569 Non-current 24,555 86,369 487 3,021 41,064 Equity 582,343 1,093,225 96,188 205,297 132,720 Accumulated non-controlling 328,302 339,067 53,053 53,146 103,468 Operating revenue 687,752 3,628,995 69,234 227,884 317,591 Profit or loss for the year 57,314 156,109 2,112 3,225 2,885 Total comprehensive income 55,586 141,719 2,362 3,036 (490 ) The profit or loss allocated to non-controlling 9,395 43,961 1,165 870 381 Cash flows from operating activities 99,269 108,203 13,895 28,320 57,262 Cash flows from investing activities (81,758 ) (568,518 ) (17,354 ) (36,086 ) (43,483 ) Cash flows from financing activities before dividend paid to non-controlling (19,739 ) (97,221 ) — — — Dividend paid to non-controlling (9,817 ) (29,490 ) — — — Gain or loss foreign currency translation — (184 ) — (47 ) — Net (decrease)/increase in cash and cash equivalents (2,228 ) (557,536 ) (3,459 ) (7,766 ) 13,779 38.3 Transactions with Non-controlling The effect of changes in the ownership interest on the equity attributable to owners of the Group during 2015, 2016 and 2017 is summarized as follows: (in millions of Korean won) 2015 2016 2017 Carrying amount of non-controlling ￦ — ￦ 4,022 ￦ (732 ) Consideration paid to non-controlling 2,699 7,347 6,173 Excess of consideration paid recognized in parent’s equity ￦ 2,699 ￦ 11,369 ￦ 5,441

Events after Reporting Period

Events after Reporting Period	12 Months Ended
	Dec. 31, 2017
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Events after Reporting Period	39. Events after Reporting Period Subsequent to the reporting period, public bonds issued are as follow: December 31, 2017 (in millions of Korean won) Issue date Carrying amount Interest rate Redemption date The 190-1st 2018.01.30 110,000 2.55 % 2021.01.29 The 190-2nd Public bond 2018.01.30 150,000 2.75 % 2023.01.30 The 190-3rd 2018.01.30 170,000 2.95 % 2028.01.30 The 190-4th 2018.01.30 70,000 2.93 % 2038.01.30 In accordance with a resolution of the board of directors on April 9, 2018, the Group decided to take over unmanned security business of SG Safety Corporation for the consideration of ￦

Significant Accounting Polici46

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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Basis of Preparation	2.1 Basis of Preparation The consolidated financial statements of the Group have been prepared in accordance with International Financial Reporting Standards(“IFRS”) as issued by the International Accounting Standards Board (“IASB”). The preparation of the consolidated financial statements requires the use of certain critical accounting estimates. It also requires management to exercise judgment in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgment or complexity, or areas where assumptions and estimates are significant to the consolidated financial statements are disclosed in Note 3.
Changes in Accounting Policy and Disclosures	2.2 Changes in Accounting Policy and Disclosures (1) New standards and amendments adopted by the Group The Group has applied the following standards and amendments for the first time for their annual reporting period commencing January 1, 2017. The adoption of these amendments did not have any material impact on the financial statements. - Statement of Cash Flows Amendments to IAS 7, Statement of Cash Flows non-cash - Income Tax Amendments to IAS 12 clarify how to account for deferred tax assets related to debt instruments measured at fair value. IAS 12 provides requirements on the recognition and measurement of current or deferred tax liabilities or assets. The amendments issued clarify the requirements on recognition of deferred tax assets for unrealized losses, to address diversity in practice - Disclosures of Interests in Other Entities Amendments to IFRS 12 clarify when an entity’s interest in a subsidiary, a joint venture or an associate is classified as held for sales in accordance with IFRS 5, the entity is required to disclose other information except for summarized financial information in accordance with IFRS 12. (2) New standards, amendments and interpretations not yet adopted Certain new accounting standards and interpretations that have been published that are not mandatory for annual reporting period commencing January 1, 2017 and have not been early adopted by the Group are set out below. - Amendments to IAS 28, Investments in Associates and Joint Ventures When an investment in an associate or a joint venture is held by, or it held indirectly through, an entity that is a venture capital organization, or a mutual fund, unit trust and similar entities including investment-linked insurance funds, the entity may elect to measure that investment at fair value through profit or loss in accordance with IFRS 9. The amendments clarify that an entity shall make this election separately for each associate of joint venture, at initial recognition of the associate or joint venture. The Group will apply these amendments retrospectively for annual periods beginning on or after January 1, 2018, and early adoption is permitted. The Group does not expect the amendments to have a significant impact on the financial statements. - Amendment to IAS 40, Transfers of Investment Property Paragraph 57 of IAS 40 clarifies that a transfer to, or from, investment property, including property under construction, can only be made if there has been a change in use that is supported by evidence, and provides a list of circumstances as examples. The amendment will be effective for annual periods beginning on or after January 1, 2018, with early adoption permitted. The Group does not expect the amendment to have a significant impact on the financial statements. - Amendments to IFRS 2, Share-based Payment Amendments to IFRS 2 clarify accounting for a modification to the terms and conditions of a share-based payment that changes the classification of the transaction from cash-settled to equity-settled. Amendments also clarify that the measurement approach should treat the terms and conditions of a cash-settled award in the same way as for an equity-settled award. The amendments will be effective for annual periods beginning on or after January 1, 2018, with early adoption permitted. The Group does not expect the amendments to have a significant impact on the financial statements. - Enactments to IFRIC 22, Foreign Currency Transaction and Advance Consideration According to these enactments, the date of the transaction for the purpose of determining the exchange rate to use on initial recognition of the related asset, expense or income (or part of it) is the date on which an entity initially recognizes the non-monetary non-monetary - Enactment of IFRS 16, Leases IFRS 16 Leases issued on May 22, 2017 is effective for annual periods beginning on or after January 1, 2019, with early adoption permitted. This standard will replace IAS 17 Leases, IFRIC 4 Determining whether an Arrangement contains a Lease, SIC-15 SIC-27 At inception of a contract, the entity shall assess whether the contract is, or contains, a lease. Also, at the date of initial application, the entity shall assess whether the contract is, or contains, a lease in accordance with the standard. However, the entity will not need to reassess all contracts with applying the practical expedient. As practical expedient, the entity can elect to apply the new guidance regarding the definition of a lease only to contracts entered into (or changed) on or after the date of initial application. Existing lease contracts will not need to be reassessed. This expedient must be consistently applied to all contracts. For a contract that is, or contains, a lease, the entity shall account for each lease component within the contract as a lease separately from non-lease right-of-use non-lease non-lease (1) Lessee accounting A lessee shall apply this standard to its leases either: • retrospectively to each prior reporting period presented applying IAS 8 Accounting Policies, Changes in Accounting Estimates and Errors (Full retrospective application); or • retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial application. The Group has not yet elected the application method. The Group performed an impact assessment to identify potential financial effects of applying IFRS 16. The assessment was performed based on available information as at December 31, 2017 to identify effects on 2017 financial statements. The Group is analyzing the effects on the financial statements; however, it is difficult to provide reasonable estimates of financial effects until the analyses is complete. (2) Lessor accounting The Company expects the effect on the financial statements applying the new standard will not be significant - IFRS 9, Financial Instruments The new standard for financial instruments issued on September 25, 2015 are effective for annual periods beginning on or after January 1, 2018 with early application permitted. This standard will replace IAS 39, Financial Instruments: Recognition and Measurement The standard requires retrospective application with some exceptions. For example, an entity is not required to restate prior period in relation to classification and measurement (including impairment) of financial instruments. The standard requires prospective application of its hedge accounting requirements for all hedging relationships except the accounting for time value of options and other exceptions. IFRS 9, Financial Instruments An effective implementation of IFRS 9 requires preparation processes including financial impact assessment, accounting policy establishment, accounting system development and the system stabilization. The impact on the Group’s financial statements due to the application of the standard is dependent on judgements made in applying the standard, financial instruments held by the Group and macroeconomic variables. The Group performed an impact assessment to identify potential financial effects of applying IFRS 9. The assessment was performed based on available information as at December 31, 2017, and the results of the assessment are explained as below. (a) Classification and Measurement of Financial Assets When implementing IFRS 9, the classification of financial assets will be driven by the Group’s business model for managing the financial assets and contractual terms of cash flow. The following table shows the classification of financial assets measured subsequently at amortized cost, at fair value through other comprehensive income and at fair value through profit or loss. If a hybrid contract contains a host that is a financial asset, the classification of the hybrid contract shall be determined for the entire contract without separating the embedded derivative. Business model for the contractual cash flows characteristics Solely represent payments of principal and interest All other Hold the financial asset for the collection of the contractual cash flows Measured at amortized cost 1 Recognized at fair value through profit or loss 2 Hold the financial asset for the collection of the contractual cash flows and sale Recognized at fair value through other comprehensive income 1 Hold for sale Recognized at fair value through profit or loss 1 A designation at fair value through profit or loss is allowed only if such designation mitigates an accounting mismatch (irrevocable) 2 Equity investments not held for trading can be recorded in other comprehensive income (irrevocable). With the implementation of IFRS 9, the criteria to classify the financial assets at amortized cost or at fair value through other comprehensive income are more strictly applied than the criteria applied with IAS 39. Accordingly, the financial assets at fair value through profit or loss may increase by implementing IFRS 9 and may result an extended fluctuation in profit or loss. As of December 31, 2017, the Group owns loan and trade receivables of ￦ available-for-sales ￦ According to IFRS 9, a debt instrument is measured at amortized cost if: a) the objective of the business model is to hold the financial asset for the collection of the contractual cash flows, and b) the contractual cash flows under the instrument solely represent payments of principal and interest. Also, a debt instrument is measured at fair value through other comprehensive income if the objective of the business model is achieved both by collecting contractual cash flows and selling financial assets; and the contractual cash flows represents solely payments of principal and interest on a specific date under contract terms. Based on results from the impact assessment of IFRS 9, the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. According to IFRS 9, equity instruments that are not held for trading, the Group plans to elect an irrevocable election at initial recognition to classify the instruments as assets measured at fair value through other comprehensive income, which all subsequent changes in fair value being recognized in other comprehensive income and not recycled to profit or loss. As at December 31, 2017, the Group holds equity instruments of ￦ available-for-sale. According to IFRS 9, debt instruments those contractual cash flows do not represent solely payments of principal and interest and held for trading, and equity instruments that are not designated as instruments measured at fair value through other comprehensive income are measured at fair value through profit or loss. (b) Impairment: Financial Assets and Contract Assets The new impairment model requires the recognition of impairment provisions based on expected credit losses (ECL) rather than only incurred credit losses as is the case under IAS 39. It applies to financial assets classified at amortized cost, debt instruments measured at fair value through other comprehensive income, lease receivables, contract assets, loan commitments and certain financial guarantee contracts. As at December 31, 2017, the Group owns debt investment carried at amortized cost of ￦ ￦ held-to-maturity ￦ ￦ As a result of the impact assessment, the Group expects the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. (c) Hedge Accounting Hedge accounting mechanics (fair value hedges, cash flow hedges and hedge of net investments in a foreign operations) required by IAS 39 remains unchanged in IFRS 9, however, the new hedge accounting rules will align the accounting for hedging instruments more closely with the Group’s risk management practices. As a general rule, more hedge relationships might be eligible for hedge accounting, as the standard introduces a more principles-based approach. IFRS 9 allows more hedging instruments and hedged items to qualify for hedge accounting, and relaxes the hedge accounting requirement by removing two hedge effectiveness tests that are a prospective test to ensure that the hedging relationship is expected to be highly effective and a quantitative retrospective test (within range of 80-125 ￦ ￦ The Group has performed an impact assessment with an assumption that the Group applies hedge accounting in accordance with IFRS 9. As a result of the impact assessment, the Group expects the application of the new standard as at December 31, 2017 does not have a material impact on the Group’s financial statements. - IFRS 15 Revenue from Contracts with Customers The Group will apply IFRS 15 Revenue from Contracts with Customers Revenue Construction Contracts, SIC-31 , Revenue-Barter Transactions Involving Advertising Services IFRIC 13 Customer Loyalty Programs, IFRIC 15 Agreements for the Construction of Real Estate and IFRIC 18 Transfers of assets from customers Revenue from Contracts with Customers IAS 18 and other current revenue standard identify revenue as income that arises in the course of ordinary activities of an entity and provides guidance on a variety of different types of revenue, such as, sale of goods, rendering of services, interest, dividends, royalties and construction contracts. However, the new standard is based on the principle that revenue is recognized when control of a good or service transfers to a customer so the notion of control replaces the existing notion of risks and rewards. A new five-step process must be applied before revenue from contract with customers can be recognized: • Identify contracts with customers • Identify the separate performance obligation • Determine the transaction price of the contract • Allocate the transaction price to each of the separate performance obligations, and • Recognize the revenue as each performance obligation is satisfied. The Group formed a task force team since fourth quarter of 2014 for preparation of implementing IFRS 15 Revenue from Contracts with Customers. Also the Group develops the internal control system and implements accounting process system by analyzing the Group’s revenue structure with accounting experts and IT specialists. IFRS 15 will affect not only accounting treatments but also the general business practice including sales strategy and operational structures. Therefore, the Group accomplished an orientation program for both Group’s directors and employees, and periodically reported to the managements about implementation plan and progress. Group identified the following areas are likely to be affected in general. (a) Identifying performance obligations The Group provides telecommunication services and sells handsets as their main business. With the implementation of IFRS 15, the Group identifies performance obligations with a customer such as providing telecommunication services, selling handsets and other. The timing of revenue recognition depends on a performance obligation is satisfied at a point in time or over time. Where a performance obligation is satisfied over time, the related revenue is also recognized over time. (b) Allocation the transaction price and Revenue recognition With implementation of IFRS 15, the Group allocated the transaction price to each performance obligation identified in a contract based on the relative stand-alone selling prices of the goods or services being provided to the customer. To allocate the transaction price to each performance obligation on a relative stand-alone price basis, the Group determines the stand-alone selling price at contract inception of the distinct good or service underlying each performance obligation in the contract and allocate the transaction price in proportion to those stand-alone selling price. The stand-alone selling price is the price at which the Group would sell a promised good or service separately to the customer. The best evidence of a stand-alone selling price is the observable price of a good or service when the Group sells that good or service separately in similar circumstances and to similar customers. The Group recognizes the allocated amount as contract assets or contract liabilities, and amortizes it through the remaining period which is adjusted in operating income. (c) Incremental costs of obtaining a contract The Group pays the commission fees when new customer subscribe for telecommunication services. The incremental contract acquisition costs are those commission fees that the Group incurs to acquire a contract with a customer that it would not have incurred if the contract had not been acquired. According to IFRS 15, the Group recognizes as an asset the incremental contract acquisition costs and amortize it over the expected period of benefit. However, as a practical expedient, the Group may recognize the incremental contract acquisition costs as an expense when incurred if the amortization period of the asset is one year or less. With implementation of IFRS 15, the Group’s operating income and expenses are expected to be decreased. Under the modified retrospective method, we will apply the rules to all open contracts existing as of January 1, 2018, recognizing in beginning retained earnings for 2018 an adjustment between ￦ ￦
Consolidation	2.3 Consolidation The Group has prepared the consolidated financial statements in accordance with IFRS 10 Consolidated Financial Statements (1) Subsidiaries Subsidiaries are all entities over which the Group has control. The Group controls an entity when the Group is exposed to, or has rights to, variable returns from its involvement with the entity and has the ability to affect those returns through its power to direct the activities of the entity. Subsidiaries are fully consolidated from the date on which control is transferred to the Group. They are deconsolidated from the date that control ceases. The acquisition method of accounting is used to account for business combinations by the Group. The consideration transferred is measured at the fair values of the assets transferred, and identifiable assets acquired and liabilities and contingent liabilities assumed in a business combination are measured initially at their fair values at the acquisition date. The Group recognizes any non-controlling acquisition-by-acquisition non-controlling non-controlling The excess of consideration transferred, amount of any non-controlling Intercompany transactions, balances and unrealized gains on transactions between group companies are eliminated. Unrealized losses are also eliminated unless the transaction provides evidence of an impairment of the transferred asset. Accounting policies of subsidiaries have been changed where necessary to ensure consistency with the policies adopted by the Group. (2) Changes in ownership interests in subsidiaries without change of control Any difference between the amount of the adjustment to non-controlling (3) Disposal of subsidiaries When the Group ceases to consolidate for a subsidiary because of a loss of control, any retained interest in the subsidiary is remeasured to its fair value with the change in carrying amount recognized in profit or loss. (4) Associates Associates are all entities over which the Group has significant influence, and investments in associates are initially recognized at acquisition cost using the equity method. Unrealized gains on transactions between the Group and its associates are eliminated to the extent of the Group’s interest in the associates. If there is any objective evidence that the investment in the associate is impaired, the Group recognizes the difference between the recoverable amount of the associate and its book amount as impairment loss. (5) Joint arrangement A joint arrangement, wherein two or more parties have joint control, is classified as either a joint operation or a joint venture. A joint operator recognizes its direct right to the assets, liabilities, revenues and expenses of joint operations and its share of any jointly held or incurred assets, liabilities, revenues and expenses. A joint venturer has rights to the net assets relating to the joint venture and accounts for that investment using the equity method.
Segment Reporting	2.4 Segment Reporting Information of each operating segment is reported in a manner consistent with the business segment reporting provided to the chief operating decision-maker (Note 33). The chief operating decision-maker is responsible for allocating resources and assessing performance of the operating segments.
Foreign Currency Translation	2.5 Foreign Currency Translation (1) Functional and presentation currency Items included in the financial statements of each of the Group’s entities are measured using the currency of the primary economic environment in which the each entity operates (the “functional currency’). The consolidated financial statements are presented in Korean won, which is the Controlling Company’s functional and presentation currency. (2) Transactions and balances Foreign currency transactions are translated into the functional currency using the exchange rates at the dates of the transactions. Foreign exchange gains and losses resulting from the settlement of such transactions and from the translation of monetary assets and liabilities denominated in foreign currencies at year end exchange rates are generally recognized in profit or loss. Non-monetary non-monetary non-monetary available-for-sale (3) Translation to the presentation currency The results and financial position of foreign operations that have a functional currency different from the presentation currency are translated into the presentation currency as follows: • assets and liabilities for each statement of financial position presented are translated at the closing rate at the end of the reporting period, • income and expenses for each statement of profit or loss are translated at average exchange rates for the period, • equity is translated at the historical exchange rate, and • all resulting exchange differences are recognized in other comprehensive income.
Cash and Cash Equivalents	2.6 Cash and Cash Equivalents Cash and cash equivalents include cash on hand, deposits held at call with banks, and other short-term highly liquid investments with original maturities of less than three months.
Financial Assets	2.7 Financial Assets (1) Classification and measurement The Group classifies its financial assets into the following categories: financial assets at fair value through profit or loss, available-for-sale held-to-maturity The Group may designate the entire hybrid (combined) contract as a financial asset at fair value through profit or loss for a contract that contains one or more embedded derivatives. At initial recognition, the Group measures a financial asset at its fair value plus, in the case of a financial asset not at fair value through profit or loss, transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at fair value through profit or loss are expensed in profit or loss. Available-for-sale held-to-maturity Gains or losses arising from changes in the fair value of financial assets at fair value through profit or loss are recognized in profit or loss within other income or other expenses. Gains or losses arising from changes in the available-for-sale (2) Impairment The Group assesses at the end of each reporting period whether there is objective evidence that a financial asset or a group of financial assets is impaired. A financial asset or a group of financial assets is impaired and impairment losses are incurred only if there is objective evidence of impairment as a result of one or more events that occurred after the initial recognition of the asset (a ‘loss event’) and that loss event (or events) has an impact on the estimated future cash flows of the financial asset or a group of financial assets that can be reliably estimated. Impairment of loans and receivables is presented as a deduction in an allowance account. Impairment of other financial assets is directly deducted from their carrying amount. The Group writes off financial assets when the assets are determined to be no longer recoverable. The criteria that the Group uses to determine that there is objective evidence of an impairment loss include: • Significant financial difficulty of the issuer or obligor; • A breach of contract, such as a default or delinquency in interest or principal payments; • For economic or legal reasons relating to the borrower’s financial difficulty, granting to the borrower a concession that the lender would not otherwise consider; • It becomes probable that the borrower will enter bankruptcy or other financial reorganization; • The disappearance of an active market for that financial asset because of financial difficulties; or • Observable data indicating that there is a measurable decrease in the estimated future cash flows from a portfolio of financial assets since the initial recognition of those assets, although the decrease cannot yet be identified with the individual financial assets in the portfolio. (3) Derecognition If the Group transfers a financial asset and the transfer does not result in derecognition because the Group has retained substantially of all risks and rewards of ownership of the transferred asset due to a recourse in the event the debtor defaults, the Group continues to recognize the transferred asset in its entirety and recognizes a financial liability for the consideration received. The related financial liability is classified as ‘borrowings’ in the statement of financial position. (4) Offsetting of financial instruments Financial assets and liabilities are offset and the net amount reported in the statements of financial position where there is a legally enforceable right to offset the recognized amounts and there is an intention to settle on a net basis or realize the assets and settle the liability simultaneously. The legally enforceable right must not be contingent on future events and must be enforceable in the normal course of business and in the event of default, insolvency or bankruptcy of the Group or the counterparty.
Derivative Instruments	2.8 Derivative Instruments Derivatives are initially recognized at fair value on the date when a derivative contract is entered into and are subsequently remeasured at their fair value. Changes in the fair value of the derivatives that are not qualified for hedge accounting are recognized in the statement of profit or loss within ‘other income (expenses)’ and ‘finance income (expenses)’ according to the nature of transactions. If the Group uses a valuation technique that incorporates data not obtained from observable markets for the fair value at initial recognition of the financial instrument, there may be a difference between the transaction price and the amount determined using that valuation technique (Day 1 profit and loss). In these circumstances, the fair value of the financial instrument is recognized as the transaction price and the difference is amortized by using the straight-line method over the life of the financial instrument. If the fair value of the financial instrument is subsequently determined using observable market inputs, the remaining deferred amount is recognized in profit or loss in the statement of profit or loss. The Group applies cash flow hedge accounting to hedge the risks of foreign exchange and interest rates of the variable rate foreign currency bonds. The effective portion of changes in the fair value of derivatives that are designated and qualify as cash flow hedges is recognized in other comprehensive income. The gain or loss relating to the ineffective portion is recognized immediately as finance income (expenses) in the statement of profit or loss. Amounts of changes in fair value of effective hedging instruments accumulated in other comprehensive income are recognized as ‘finance income (expenses)’ for the periods when the corresponding transactions affect profit or loss. When a forecast transaction is no longer expected to occur, the cumulative gain or loss that is reported in other comprehensive income is recognized as ‘finance income (expenses)’. If the hedge no longer meets the criteria for hedge accounting, the adjustment to the carrying amount of a hedged item for which the effective interest method is used is amortized to profit or loss over the period to maturity.
Inventories	2.9 Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined using the moving average method, except for inventories in-transit
Non-current Assets (or Disposal Group) Held-for-sale	2.10 Non-current Held-for-sale Non-current held-for-sale
Property and Equipment	2.11 Property and Equipment Property and equipment are stated at its cost less accumulated depreciation and accumulated impairment losses. Historical cost includes expenditures that is directly attributable to the acquisition of the items. Depreciation of all property, plant, and equipment, except for land is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives, as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) Others 2 – 40 years Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years The depreciation method, residual values and useful lives of property and equipment are reviewed at the end of each reporting period and, if appropriate, accounted for as changes in accounting estimates.
Investment Property	2.12 Investment Property Investment property is a property held to earn rentals or for capital appreciation. An investment property is measured initially at its cost. After recognition as an asset, investment property is carried at cost less accumulated depreciation and impairment losses. Investment property, except for land, is depreciated using the straight-line method over their useful lives from 10 to 40 years.
Intangible Assets	2.13 Intangible Assets (1) Goodwill Goodwill is measured as explained in Note 2.3 (1) and goodwill arising from acquisition of subsidiaries and business are included in intangible assets. Goodwill is tested annually for impairment and carried at cost less accumulated impairment losses. (2) Intangible assets except goodwill Intangible assets, except for goodwill, are initially recognized at its historical cost, and carried at cost less accumulated amortization and accumulated impairment losses. Membership rights (condominium membership and golf membership) and broadcast rights that have an indefinite useful life are not subject to amortization because there is no foreseeable limit to the period over which the assets are expected to be utilized. The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 6 years Frequency usage rights 5 –10 years Others 1 2 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life.
Borrowing Costs	2.14 Borrowing Costs General and specific borrowing costs that are directly attributable to the acquisition, construction or production of a qualifying asset are capitalized during the period of time that is required to complete and prepare the asset for its intended use or sale. Investment income earned on the temporary investment of specific borrowings pending their expenditure on qualifying assets is deducted from the borrowing costs eligible for capitalization. Other borrowing costs are expensed in the period in which they are incurred.
Government Grants	2.15 Government Grants Grants from the government are recognized at their fair value where there is a reasonable assurance that the grant will be received and the Group will comply with all attached conditions. Government grants related to assets are presented in the statement of financial position by setting up the grant as deferred income that is recognized in profit or loss on a systematic basis over the useful life of the asset. Grants related to income are presented as a credit in the statement of profit or loss within ‘other income’.
Impairment of Non-Financial Assets	2.16 Impairment of Non-Financial Goodwill and intangible assets that have an indefinite useful life are not subject to amortization and are tested annually for impairment, or more frequently if events or changes in circumstances indicate that they might be impaired. Other assets are tested for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. An impairment loss is recognized for the amount by which the asset’s carrying amount exceeds its recoverable amount. The recoverable amount is the higher of an asset’s fair value less costs to sell and value in use. Non-financial
Financial Liabilities	2.17 Financial Liabilities (1) Classification and measurement The Group’s financial liabilities at fair value through profit or loss are financial instruments held for trading and designated as financial liabilities at fair value through profit or loss. Financial liabilities held for trading are financial liabilities that are incurred principally for the purpose of repurchasing them in the near term and derivatives that are not designated as hedges or bifurcated from financial instruments containing embedded derivatives. Financial liabilities that the Group designated as at fair value through profit or loss are structured financial liabilities containing embedded derivatives issued by the Group. As it was unable to measure the embedded derivatives separately from its host contract, the Group designated the entire hybrid contact as at fair value through profit or loss. The financial liability that the Group designated as at fair value through profit or loss is a foreign convertible bond. The Group classifies non-derivative Preferred shares that provide for a mandatory redemption at a particular date are classified as liabilities. Interest expenses on these preferred shares calculated using the effective interest method are recognized in the statement of profit or loss as ‘finance costs’, together with interest expenses recognized from other financial liabilities. (2) Derecognition Financial liabilities are removed from the statement of financial position when it is extinguished, for example, when the obligation specified in the contract is discharged or cancelled or expired or when the terms of an existing financial liability are substantially modified.
Financial Guarantee Contracts	2.18 Financial Guarantee Contracts Financial guarantees contracts provided by the Group are initially measured at fair value on the date the guarantee was given. Subsequent to initial recognition, the Group’s liabilities under such guarantees are measured at the higher of the amounts below and recognized as ‘other financial liabilities’: • the amount determined in accordance with IAS 37 Provisions, Contingent Liabilities and Contingent Assets; or • the amount initially recognized less cumulative amortization in accordance with IAS 18 Revenue.
Compound Financial Instruments	2.19 Compound Financial Instruments Compound financial instruments are convertible bonds that can be converted into equity instruments at the option of the holder. The liability component of a compound financial instrument is recognized initially at the fair value of a similar liability that does not have an equity conversion option. The equity component is recognized initially on the difference between the fair value of the compound financial instrument as a whole and the fair value of the liability component. Any directly attributable transaction costs are allocated to the liability and equity components in proportion to their initial carrying amounts.
Employee Benefits	2.20 Employee Benefits (1) Post-employment benefits The Group operates both defined benefit and defined contribution plans. A defined contribution plan is a pension plan under which the Group pays fixed contributions into a separate entity. The contributions are recognized as employee benefit expenses when an employee has rendered service. A defined benefit plan is a pension plan that is not a defined contribution plan. Generally, post-employment benefits are payable after the completion of employment, and the benefit amount depended on the employee’s age, periods of service or salary levels. The liability recognized in the statement of financial position in respect of defined benefit pension plans is the present value of the defined benefit obligation at the end of the reporting period less the fair value of plan assets. The defined benefit obligation is calculated annually by independent actuaries using the projected unit credit method. The present value of the defined benefit obligation is determined by discounting the estimated future cash outflows using interest rates of high-quality corporate bonds that are denominated in the currency in which the benefits will be paid, and that have terms approximating to the terms of the related obligation. Remeasurement gains and losses arising from experience adjustments and changes in actuarial assumptions are recognized in the period in which they occur, directly in other comprehensive income. Changes in the present value of the defined benefit obligation resulting from plan amendments or curtailments are recognized immediately in profit or loss as past service costs. (2) Termination benefits Termination benefits are payable when employment is terminated by the Group before the normal retirement date, or whenever an employee accepts voluntary redundancy in exchange for these benefits. The Group recognizes termination benefits at the earlier of the following dates: when the entity can no longer withdraw the offer of those benefits or when the entity recognizes costs for a restructuring.
Share-based payments	2.21 Share-based payments Equity-settled share-based payment is recognized at fair value of equity instruments on grant date, and employee benefit expense is recognized over the vesting period. At the end of each period, the Group revises its estimates of the number of options that are expected to vest based on the non-market When the options are exercised, the Group issues new shares. The proceeds received, net of any directly attributable transaction costs, are recognized as share capital (nominal value) and share premium.
Provisions	2.22 Provisions Provisions are measured at the present value of the expenditures expected to be required to settle the obligation, and the increase in the provision due to passage of time is recognized as interest expense.
Leases	2.23 Leases (1) Lessee A lease is an agreement, whereby the lessor conveys to the lessee, in return for a payment or series of payments, the right to use an asset for an agreed period of time. Leases where all the risks and rewards of ownership are not transferred to the Group are classified as operating leases. Lease payments under operating leases are recognized as expenses on a straight-line basis over the lease term. Leases where the Group has substantially all the risks and rewards of ownership are classified as finance leases. Finance leases are capitalized as lease assets and liabilities at the lease’s inception at the fair value of the leased property or, if lower, the present value of the minimum lease payments. (2) Lessor A lease is classified as a finance lease if it transfers substantially all the risks and rewards incidental to ownership at the inception of the lease. A lease other than a finance lease is classified as an operating lease. Lease income from operating leases is recognized in income on a straight-line basis over the lease term. Initial direct costs incurred by the lessor in negotiating and arranging an operating lease is added to the carrying amount of the leased asset and recognized as an expense over the lease term on the same basis as the lease income.
Share Capital	2.24 Share Capital The Group classifies ordinary shares as equity. Where the Controlling Company purchases its own shares, the consideration paid, including any directly attributable incremental costs, is deducted from equity until the share are cancelled or reissued. When these treasury shares are reissued, any consideration received is including in equity attributable to the equity holders of the Controlling Company.
Revenue Recognition	2.25 Revenue Recognition Revenue is measured at the fair value of the consideration received or receivable for the sale of goods or rendering of services arising from the normal activities of the Group. Amounts disclosed as revenue are net of value added taxes, returns, rebates and discounts and after elimination of intra-group transactions. The Group recognizes revenue when the amount of revenue can be reliably measured; when it is probable that future economic benefits will flow to the Group; and when specific criteria have been met for each of the Group’s activities, as described below. The Group bases its estimate on historical results, taking into consideration the type of customer, the type of transaction and the specifics of each arrangement. (1) Rendering of Services When providing interconnection or telecommunications service to a customer based on service plans, the related revenue is recognized at the time service is provided. When providing the telecommunications equipment rental service to a customer based on service plans, the related revenue is recognized on straight-line basis over the contract period. Revenue related to the other telecommunications services is recognized when the service is provided to the customer. For other services, when the outcome of a transaction involving the rendering of services can be estimated reliably, revenue associated with such a transaction is recognized by reference to the stage of performance of the services. When the outcome of the transaction involving the rendering of services cannot be estimated reliably, revenue is recognized only to the extent of the expenses recognized that are recoverable. Total consideration for combined services is allocated to each service in proportion to its fair value and the allocated amount is recognized as revenue according to revenue recognition policy for the service. (2) Sales of goods The Group sells a range of handsets. Revenue from the sale of goods is recognized when products are delivered to the purchaser. (3) Interest income Interest income is recognized using the effective interest method according to the time passed. When a loan and receivable is impaired, the Group reduces the carrying amount to its recoverable amount and continues unwinding the discount as interest income. Interest income on impaired loans and receivables is recognized using the original effective interest rate. (4) Commission fees Commission fees related to credit card business are recognized when it is probable that future economic benefits will flow to the entity and these benefits can be reliably measured. Revenues from acquiree fee, agent fee, optional service fees, member service fees and credit card service charge are measured at the fair value of the consideration received and recognized on an accrual basis. (5) Royalty income Royalty income is recognized on an accrual basis in accordance with the substance of the relevant agreements. (6) Dividend income Dividend income is recognized when the right to receive payment is established. (7) Customer loyalty program The Group operates a customer loyalty program where customers accumulate points for purchases made which entitle them to discounts on future purchases. The reward points are recognized as a separately identifiable component of the initial sale transaction. The fair value of the consideration received or receivable in respect of the initial sale is allocated between the reward points and the other components of the sale. The fair value of the reward points is measured by taking into account the proportion of the reward points that are not expected to be redeemed by customers. Revenue from the reward points is recognized when the points are redeemed.
Current and Deferred Income Tax	2.26 Current and Deferred Income Tax The tax expense for the period consists of current and deferred tax. Tax is recognized on the profit for the period in the statement of profit or loss, except to the extent that it relates to items recognized in other comprehensive income or directly in equity. In this case, the tax is also recognized in other comprehensive income or directly in equity, respectively. The tax expense is calculated on the basis of the tax laws enacted or substantively enacted at the end of the reporting period. Management periodically evaluates tax policies that are applied in tax returns in which applicable tax regulation is subject to interpretation. The Group recognizes current income tax on the basis of the amount expected to be paid to the tax authorities. Deferred tax is recognized for temporary differences arising between the tax bases of assets and liabilities and their carrying amounts as expected tax consequences at the recovery or settlement of the carrying amounts of the assets and liabilities. However, deferred tax assets and liabilities are not recognized if they arise from initial recognition of an asset or liability in a transaction other than a business combination that at the time of the transaction affects neither accounting nor taxable profit or loss. Deferred tax assets are recognized only if it is probable that future taxable amount will be available to utilize those temporary differences and losses. Deferred tax liability is recognized for taxable temporary differences associated with investments in subsidiaries, associates, and interests in joint ventures, except to the extent that the Group is able to control the timing of the reversal of the temporary difference and it is probable that the temporary difference will not reverse in the foreseeable future. In addition, deferred tax asset is recognized for deductible temporary differences arising from such investments to the extent that it is probable the temporary difference will reverse in the foreseeable future and taxable profit will be available against which the temporary difference can be utilized. Deferred tax assets and liabilities are offset when there is a legally enforceable right to offset current tax assets against current tax liabilities and when the deferred income taxes assets and liabilities relate to income taxes levied by the same taxation authority on either the same taxable entity or different taxable entities where there is an intention to settle the balances on a net basis.
Dividend	2.27 Dividend Dividend distribution to the Group’s shareholders is recognized as a liability in the financial statements in the period in which the dividends are approved by the Group’s shareholders.
Approval of Issuance of the Financial Statements	2.28 Approval of Issuance of the Financial Statements The issuance of the December 31, 2017 consolidated financial statements of the Group was approved by the Board of Directors on April 27, 2018.

General Information (Tables)

General Information (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Consolidated Subsidiaries	The consolidated subsidiaries as of December 31, 2016 and 2017, are as follows: Controlling percentage 1 Subsidiary Type of Business Location December 31, December 31, Closing KT Powertel Co., Ltd. 2 Trunk radio system business Korea 44.8% 44.8% December KT Linkus Co., Ltd. Public telephone maintenance Korea 91.4% 91.4% December KT Submarine Co., Ltd. 2,3 Submarine cable construction and maintenance Korea 39.3% 39.3% December KT Telecop Co., Ltd. Security service Korea 86.8% 86.8% December KT Hitel Co., Ltd. Data communication Korea 67.1% 67.1% December KT Service Bukbu Co., Ltd. Opening services of fixed line Korea 67.3% 67.3% December KT Service Nambu Co., Ltd. Opening services of fixed line Korea 77.3% 77.3% December KT Commerce Inc. B2C, B2B service Korea 100.0% 100.0% December KT New Business Fund No.1 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.1 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.2 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.3 Investment fund Korea 100.0% 100.0% December KT Strategic Investment Fund No.4 Investment fund Korea — 100.0% December BC Card Co., Ltd. Credit card business Korea 69.5% 69.5% December VP Inc. Payment security service for credit card, others Korea 50.9% 50.9% December H&C Network Call centre for financial sectors Korea 100.0% 100.0% December BC Card China Co., Ltd. Software development and data processing China 100.0% 100.0% December INITECH Co., Ltd. 4 Internet banking ASP and security solutions Korea 58.2% 58.2% December Smartro Co., Ltd. VAN (Value Added Network) business Korea 81.1% 81.1% December KTDS Co., Ltd. 4 System integration and maintenance Korea 95.5% 95.5% December KT M Hows Co., Ltd. Mobile marketing Korea 90.0% 90.0% December KT M&S Co., Ltd. PCS distribution Korea 100.0% 100.0% December GENIE Music Corporation(KT Music Corporation) 2 Online music production and distribution Korea 49.9% 42.5% December KT Skylife Co., Ltd. 4 Satellite broadcasting business Korea 50.3% 50.3% December Skylife TV Co., Ltd. TV contents provider Korea 92.6% 92.6% December KT Estate Inc. Residential building development and supply Korea 100.0% 100.0% December KT AMC Co., Ltd. Asset management and consulting services Korea 100.0% 100.0% December NEXR Co., Ltd. Cloud system implementation Korea 100.0% 100.0% December KTSB Data service Data centre development and related service Korea 51.0% 51.0% December KT Sat Co., Ltd. Satellite communication business Korea 100.0% 100.0% December KT Innoedu Co E-learning business Korea 96.8% — December Nasmedia, Inc. 3 Online advertisement Korea 42.8% 42.8% December KT Sports Management of sports group Korea 100.0% 100.0% December KT Music Contents Fund No.1 Music contents investment business Korea 80.0% 80.0% December KT Music Contents Fund No.2 Music contents investment business Korea — 100.0% December KT-Michigan Content investment business Korea 88.6% 88.6% December Autopion Co., Ltd. Service for information and communication Korea 100.0% 100.0% December KTCS Corporation 2,4 Database and online information provider Korea 30.9% 30.9% December KTIS Corporation 2,4 Database and online information provider Korea 30.1% 30.1% December KT M mobile Special category telecommunications operator and sales of communication device Korea 100.0% 100.0% December KT Investment Co., Ltd. Technology business finance Korea 100.0% 100.0% December NgenBio Medicine and Pharmacy development business Belgium 49.8% — December Whowho&Company Co., Ltd. Software development and supply Korea 100.0% 100.0% December PlayD Co., Ltd. (N Search Marketing Co., Ltd.) Advertising agency business Korea 100.0% 100.0% December KT Rwanda Networks Ltd. Network installation and management Rwanda 51.0% 51.0% December AOS Ltd. System integration and maintenance Rwanda 51.0% 51.0% December KT Belgium Foreign investment business Belgium 100.0% 100.0% December KT ORS Belgium Foreign investment business Belgium 100.0% 100.0% December Korea Telecom Japan Co., Ltd. Foreign telecommunication business Japan 100.0% 100.0% December KBTO sp.zo.o. Electronic communication business Poland 75.0% 94.0% December Korea Telecom China Co., Ltd. Foreign telecommunication business China 100.0% 100.0% December KT Dutch B.V Super iMax and East Telecom management Netherlands 100.0% 100.0% December Super iMax LLC Wireless high speed internet business Uzbekistan 100.0% 100.0% December East Telecom LLC Fixed line telecommunication business Uzbekistan 91.0% 91.0% December Korea Telecom America, Inc. Foreign telecommunication business USA 100.0% 100.0% December PT. KT Indonesia Foreign telecommunication business Indonesia 99.0% 99.0% December PT. BC Card Asia Pacific Software development and supply Indonesia 99.9% 99.9% December KT Hongkong Telecommunications Co., Ltd. Fixed line communication business Hong Kong 100.0% 100.0% December KT Hong kong Limited Foreign investment business Hong Kong 100.0% 100.0% December Korea Telecom Singapore Pte.Ltd. Foreign investment business Singapore 100.0% 100.0% December Texnoprosistem LLP. Fixed line internet business Uzbekistan 100.0% 100.0% December 1 Sum of the ownership interests owned by the Controlling Company and subsidiaries. 2 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company can exercise the majority voting rights in its decision-making process at all times considering the historical voting pattern at the shareholders’ meetings. 3 Although the Controlling Company owns less than 50% ownership in this entity, this entity is consolidated as the Controlling Company holds the majority of voting right based on an agreement with other investors. 4 The number of subsidiaries’ treasury stock is deducted from the total number of shares when calculating the controlling percentage ownership. Changes in scope of consolidation in 2017 are as follows: Changes Location Subsidiary Reason Included Korea KT Strategic Investment Fund No.4 Newly established KT Music Contents Investment Fund No.2 Newly established Excluded Korea KT Innoedu Co., Ltd. Shares disposed NgeneBio Percentage of ownership decreased Summarized information for consolidated subsidiaries as of and for the years ended December 31, 2015, 2016 and 2017, follows: (in millions of Korean won) 2015 Total assets Total Operating Profit (loss) For the year KT Powertel Co., Ltd. ￦ 113,515 ￦ 21,182 ￦ 104,527 ￦ (32,417 ) KT Linkus Co., Ltd. 77,141 65,745 116,095 3,449 KT Submarine Co., Ltd. 160,314 63,518 67,268 4,145 KT Telecop Co., Ltd. 269,191 134,966 302,844 (7,593 ) KT Hitel Co.,Ltd. 235,757 33,938 162,155 7,258 KT Service Bukbu Co., Ltd 2 31,879 22,627 89,498 (4,630 ) KT Service Nambu Co., Ltd 2 20,729 10,567 110,129 (5,055 ) BC Card Co., Ltd. 1 2,963,952 1,945,634 3,504,946 218,969 H&C Network 1 248,189 70,635 241,008 19,513 Nasmedia, Inc. 141,733 72,202 45,630 9,916 KTDS Co., Ltd. 1 162,518 116,654 423,015 12,836 KT M Hows Co., Ltd. 25,093 17,980 19,352 1,728 KT M&S Co., Ltd. 256,246 217,892 853,011 (18,776 ) GENIE Music Corporation(KT Music Corporation) 90,518 30,704 90,005 3,446 KT Skylife Co., Ltd. 1 711,294 217,850 668,521 72,987 KT Estate Inc. 1 1,603,438 260,292 254,776 27,487 KTSB Data service 23,063 1,730 4,390 (2,444 ) KT Innoedu Co., Ltd. 5,858 7,585 18,156 (4,288 ) KT Sat Co., Ltd. 679,959 210,110 133,326 27,174 KT Sports 15,341 11,643 51,801 (3,836 ) KT Music Contents Fund No.1 10,206 47 468 (111 ) KT-Michigan 5,401 — 861 (209 ) Autopion Co., Ltd. 7,102 3,317 10,585 1,123 KT M mobile 64,756 13,121 42,478 (36,725 ) KT Investment Co., Ltd 49,485 30,827 4,704 (219 ) NgeneBio 7,894 4,683 — (434 ) KTCS Corporation 1 346,949 194,367 1,066,556 13,685 KTIS Corporation 211,164 55,370 473,892 15,041 Korea Telecom Japan Co., Ltd. 13,889 14,393 25,652 (248 ) Korea Telecom China Co., Ltd. 909 198 1,748 (95 ) KT Dutch B.V. 1 29,402 27 161 118 Super iMax LLC 14,962 8,186 8,291 (2,220 ) East Telecom LLC 30,833 17,066 24,066 664 Korea Telecom America, Inc. 6,016 1,378 6,391 156 PT. KT Indonesia 22 — — (9 ) Olleh Rwanda Networks Ltd. 188,951 147,653 7,299 (28,721 ) KT Belgium 77,058 4 — (127 ) KT ORS Belgium 1,996 20 — (75 ) KBTO sp.zo.o. 1,471 1,817 — (328 ) Africa Olleh Services Ltd. 11,928 12,187 8,712 (923 ) (In millions of Korean won) 2016 Total assets Total liabilities Operating Profit (loss) For the year KT Powertel Co., Ltd. ￦ 113,725 ￦ 19,899 ￦ 81,390 ￦ 202 KT Linkus Co., Ltd. 64,318 56,953 117,587 (3,830 ) KT Submarine Co., Ltd. 156,993 55,573 84,137 5,146 KT Telecop Co., Ltd. 265,553 132,344 315,948 143 KT Hitel Co., Ltd. 249,202 46,941 198,994 4,298 KT Service Bukbu Co., Ltd. 32,863 24,580 182,952 694 KT Service Nambu Co., Ltd. 32,621 24,282 218,602 772 BC Card Co., Ltd. 1 3,651,065 2,602,404 3,567,512 163,131 H&C Network 1 272,110 80,983 266,613 14,749 Nasmedia, Inc. 1 263,925 159,502 70,037 11,972 KTDS Co., Ltd. 1 197,970 151,644 476,379 10,838 KT M Hows Co., Ltd. 28,539 18,466 19,922 2,865 KT M&S Co., Ltd. 247,854 227,507 724,144 (12,955 ) GENIE Music Corporation(KT Music Corporation) 110,080 41,953 111,450 8,235 KT Skylife Co., Ltd. 1 777,948 231,452 668,945 68,863 KT Estate Inc. 1 1,734,729 375,341 405,417 46,815 KTSB Data service 20,075 759 5,136 (1,983 ) KT Innoedu Co., Ltd. 6,477 7,259 15,599 103 KT Sat Co., Ltd. 744,653 253,041 144,594 36,266 KT Sports 16,925 13,573 48,476 (198 ) KT Music Contents Fund No.1 10,592 331 349 103 KT-Michigan 16,250 163 133 (514 ) Autopion Co., Ltd. 6,163 2,794 7,772 (409 ) KT M mobile 131,446 20,369 112,532 (40,041 ) KT Investment Co., Ltd. 1 39,506 23,123 10,130 (1,832 ) NgeneBio 6,361 4,733 244 (1,833 ) KTCS Corporation 1 322,768 166,642 955,050 7,892 KTIS Corporation 221,176 63,871 436,914 9,991 Korea Telecom Japan Co., Ltd. 3,592 5,374 5,122 (1,391 ) Korea Telecom China Co., Ltd. 532 188 930 60 KT Dutch B.V 34,197 73 166 85 Super iMax LLC 10,308 6,734 10,759 (1,802 ) East Telecom LLC 31,885 16,554 27,492 3,257 Korea Telecom America, Inc. 4,464 1,306 7,113 181 PT. KT Indonesia 16 — — (7 ) KT Rwanda Networks Ltd. 167,112 138,651 13,435 (31,455 ) KT Belguium 79,391 7 — (67 ) KT ORS Belgium 2,013 23 — (46 ) KBTO sp.zo.o. 1,166 2,378 21 (2,587 ) AOS Ltd. 10,025 3,179 14,481 (1,123 ) KT Hongkong Telecommunications Co., Ltd. 1,571 956 1,568 120 (In millions of Korean won) 2017 Total assets Total liabilities Operating Profit (loss) for the year KT Powertel Co., Ltd. 115,125 18,937 69,234 2,112 KT Linkus Co., Ltd. 59,344 51,516 112,043 725 KT Submarine Co., Ltd. 142,797 34,056 73,985 8,243 KT Telecop Co., Ltd. 264,353 131,633 317,591 2,885 KT Hitel Co., Ltd. 258,240 52,943 227,884 3,225 KT Service Bukbu Co., Ltd. 29,281 22,096 194,837 688 KT Service Nambu Co., Ltd. 36,076 26,412 232,996 875 BC Card Co., Ltd. 1 4,048,263 2,955,038 3,628,995 156,109 H&C Network 1 273,856 65,446 277,622 16,104 Nasmedia, Inc. 1 315,967 188,197 120,667 26,676 KTDS Co., Ltd. 1 144,922 93,343 459,266 11,584 KT M Hows Co., Ltd. 42,738 28,489 24,610 4,097 KT M&S Co., Ltd. 242,388 231,151 734,420 (9,707 ) GENIE Music Corporation(KT Music Corporation) 139,686 48,512 156,163 (3,401 ) KT Skylife Co., Ltd. 1 792,893 210,550 687,752 57,314 KT Estate Inc. 1 1,869,194 502,915 428,446 52,416 KTSB Data service 18,306 605 4,950 (1,651 ) KT Sat Co., Ltd. 742,391 220,804 147,649 29,601 KT Sports 11,131 7,805 53,357 (199 ) KT Music Contents Fund No.1 13,804 1,041 370 (499 ) KT Music Contents Fund No.2 7,500 11 — (11 ) KT-Michigan 14,575 147 159 (426 ) Autopion Co., Ltd. 6,306 3,530 6,679 (618 ) KT M mobile 93,601 21,453 159,684 (38,883 ) KT Investment Co., Ltd. 1 54,673 38,313 8,794 (619 ) KTCS Corporation 1 348,334 188,764 968,186 7,385 KTIS Corporation 223,818 62,569 438,597 8,337 Korea Telecom Japan Co., Ltd. 1 1,554 2,788 2,772 536 Korea Telecom China Co., Ltd. 665 32 1,030 348 KT Dutch B.V 30,312 50 206 169 Super iMax LLC 3,449 4,886 7,314 (4,584 ) East Telecom LLC 1 11,672 11,748 19,663 (9,118 ) Korea Telecom America, Inc. 3,694 791 6,783 109 PT. KT Indonesia 8 — — (6 ) KT Rwanda Networks Ltd. 2 151,359 139,561 15,931 (22,762 ) KT Belguium 86,455 8 49 (2 ) KT ORS Belgium 1,769 14 10 (10 ) KBTO sp.zo.o. 3,311 2,268 67 (3,456 ) AOS Ltd. 2 9,437 4,519 8,952 (682 ) KT Hongkong Telecommunications Co., Ltd. 2,578 1,497 7,304 494 1 These companies are the intermediate controlling companies of other subsidiaries and the above financial information is from their consolidated financial statements. 2 At the end of the reporting period, convertible preferred stock issued by subsidiaries included in liabilities.

Significant Accounting Polici48

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Estimated Useful Lives of Property, Plant and Equipment	Depreciation of all property, plant, and equipment, except for land is calculated using the straight-line method to allocate their cost, net of their residual values, over their estimated useful lives, as follows: Estimated Useful Life Buildings 5 – 40 years Structures 5 – 40 years Machinery and equipment (Telecommunications equipment and others) Others 2 – 40 years Vehicles 4 – 6 years Tools 4 – 6 years Office equipment 2 – 6 years
Summary of Amortization of Intangible Assets With Limited Useful Life	The Group amortizes intangible assets with a limited useful life using the straight-line method over the following periods: Estimated Useful Life Development costs 5 – 6 years Software 6 years Frequency usage rights 5 –10 years Others 1 2 – 50 years 1 Membership rights (condominium membership and golf membership) and broadcast license included in others are classified as intangible assets with indefinite useful life.

Financial Instruments by Cate49

Financial Instruments by Category (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Financial Instruments by Category	Financial instruments by category as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Financial assets Loans and receivables Assets at fair and loss Derivatives Available- for-sale Held-to- Maturity Total Cash and cash equivalents ￦ 2,900,311 ￦ — ￦ — ￦ — ￦ — ￦ 2,900,311 Trade and other receivables 6,036,363 — — — — 6,036,363 Other financial assets 716,769 6,277 227,318 404,774 30,143 1,385,281 (In millions of Korean won) 2016 Financial liabilities Liabilities at Derivatives used for Financial Total Trade and other payables ￦ — ￦ — ￦ 8,328,082 ￦ 8,328,082 Borrowings — — 8,120,791 8,120,791 Other financial liabilities 1,973 14,928 91,763 108,664 (In millions of Korean won) 2017 Financial assets Loans and receivables Assets at fair and loss Derivatives Available- for-sale Held-to- Maturity Total Cash and cash equivalents ￦ 1,928,182 ￦ — ￦ — ￦ — ￦ — ￦ 1,928,182 Trade and other receivables 6,643,115 — — — — 6,643,115 Other financial assets 1,333,317 5,813 7,389 380,953 151 1,727,623 (In millions of Korean won) 2017 Financial liabilities Liabilities at Derivatives used for Financial Total Trade and other payables ￦ — ￦ — ￦ 8,425,503 ￦ 8,425,503 Borrowings — — 6,683,662 6,683,662 Other financial liabilities 5,051 93,770 87,669 186,490
Summary of Gains or Losses Arising From Financial Instruments by Category	Gains or losses arising from financial instruments by category for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Loans and receivables Interest income 1, 4 ￦ 85,603 ￦ 129,813 ￦ 108,608 Loss on foreign currency transaction (365 ) (7,493 ) (11,949 ) Gain(loss) on foreign currency translation 1,921 3,083 (12,354 ) Loss on disposal (2,539 ) (15,838 ) (20,351 ) Loss on valuation (141,555 ) (92,589 ) (44,219 ) Assets at fair value through profit or loss Dividend income — — 1 Gain on disposal 368 186 153 Loss on valuation — (7,184 ) (464 ) Derivatives used for hedging Loss on transaction (5,157 ) — (58,569 ) Gain(loss) on valuation 141,512 109,436 (63,640 ) Other comprehensive income for the year 2 100,401 60,501 (44,429 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (88,003 ) (71,915 ) 50,231 Available-for-sale Interest income 1,4 73 40 453 Dividend income 7,733 3,926 5,174 Gain on disposal 131,045 22,695 89,598 Impairment loss (1,471 ) (966 ) (6,137 ) Other comprehensive income for the year 2 47,381 10,925 51,235 Reclassified to profit or loss from other comprehensive income for the year 2 (83,397 ) (3,840 ) (55,450 ) Held-to-Maturity Interest income 1,4 226 213 — Liabilities at fair value through profit and loss Gain(loss) on disposal (850 ) (632 ) — Gain(loss) on valuation (2,006 ) 33 (3,078 ) Derivatives used for hedging Gain(loss) on transactions (273 ) 8,329 — Loss on valuation (1,733 ) (138 ) (145,885 ) Other comprehensive income for the year 2 11,513 4,295 (66,624 ) Reclassified to profit or loss from other comprehensive income for the year 2,3 (9,959 ) (3,956 ) 91,698 Financial liabilities at amortized cost Interest expense 4 (385,925 ) (337,219 ) (302,464 ) Gain(loss) foreign currency transaction (23,416 ) (7,518 ) 62,347 Gain(loss) foreign currency translation (166,254 ) (112,864 ) 225,695 Total ￦ (385,127 ) ￦ (308,677 ) ￦ (150,420 ) 1 BC Card, a subsidiary of the Group, recognized interest income as operating revenue. Interest income recognized as operating revenue is ￦ ￦ ￦ 2 The amounts directly reflected in equity after adjustments of deferred income tax. 3 During the year, certain derivatives of the Group were settled and the related gain or loss on valuation of cash flow hedge in other comprehensive income was reclassified to profit or loss for the year. 4 BC Card recognized gain/loss on foreign currency transaction as operating income and expenses. During the year, related gain/loss on foreign currency transaction recognized as operating income and expense is ￦ ￦

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Restricted Cash and Cash Equivalents	Restricted cash and cash equivalents as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) Type 2016 2017 Description Restricted cash and cash equivalents Restricted deposit ￦ ￦ Deposit restricted for governmental project and others

Trade and Other Receivables (Ta

Trade and Other Receivables (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Trade and Other Receivables	Trade and other receivables as of December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Total Allowance doubtful Present value Carrying amount Current assets Trade receivables ￦ 3,161,234 ￦ (470,239 ) ￦ (5,343 ) ￦ 2,685,652 Other receivables 2,763,942 (121,972 ) (270 ) 2,641,700 ￦ 5,925,176 ￦ (592,211 ) ￦ (5,613 ) ￦ 5,327,352 Non-current assets Trade receivables ￦ 263,367 ￦ (632 ) ￦ (12,835 ) ￦ 249,900 Other receivables 507,251 (19,644 ) (28,496 ) 459,111 770,618 (20,276 ) (41,331 ) 709,011 2017 (In millions of Korean won) Total Allowance doubtful Present value Carrying amount Current assets Trade receivables ￦ 3,286,169 ￦ (438,817 ) ￦ (7,508 ) ￦ 2,839,844 Other receivables 3,041,028 (66,402 ) (187 ) 2,974,439 ￦ 6,327,197 ￦ (505,219 ) ￦ (7,695 ) ￦ 5,814,283 Non-current assets Trade receivables ￦ 366,107 ￦ (610 ) ￦ (12,803 ) ￦ 352,694 Other receivables 522,459 (17,970 ) (28,351 ) 476,138 ￦ 888,566 ￦ (18,580 ) ￦ (41,154 ) ￦ 828,832
Summary of Changes in Allowance for Doubtful Accounts	Details of changes in allowance for doubtful accounts the years ended December 31, 2016 and 2017, are as follows: 2015 2016 2017 (In millions of Korean won) Trade Other Trade Other Trade Other Beginning balance ￦ 527,617 ￦ 311,082 ￦ 468,741 ￦ 250,842 ￦ 470,871 ￦ 141,616 Provision 95,489 46,066 84,975 7,736 38,888 5,809 Reversal or written-off (135,318 ) (33,282 ) (80,518 ) (108,638 ) (70,121 ) (61,220 ) Changes in the scope of consolidation (16,752 ) (69,732 ) 215 56 (107 ) (35 ) Others (2,232 ) (3,272 ) (2,542 ) (8,380 ) (104 ) (1,798 ) Ending balance ￦ 468,741 ￦ 250,842 ￦ 470,871 ￦ 141,616 ￦ 439,427 ￦ 84,372
Summary of Aging Analysis of Trade Receivables	Details of aging analysis of trade receivables as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Neither past due nor impaired ￦ 2,377,637 ￦ 2,661,406 Past due and impaired Up to 6 months 685,288 701,032 6 months to 12 months 87,547 70,190 Over 12 months 255,951 199,337 1,028,786 970,559 Less: Allowance for doubtful accounts (470,871 ) (439,427 ) ￦ 2,935,552 ￦ 3,192,538
Summary of Other Receivables	Details of other receivables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Loans ￦ 80,308 ￦ 84,682 Receivables 1 2,709,177 2,970,346 Accrued income 9,903 12,186 Refundable deposits 390,035 391,458 Loans receivable 10,355 34,273 Finance lease receivables 16,280 20,526 Others 26,369 21,478 Less: Allowance for doubtful accounts (141,616 ) (84,372 ) ￦ 3,100,811 ￦ 3,450,577 1 The settlement receivables of BC Card Co., Ltd. of ￦ ￦
Summary of Aging Analysis of Other Receivables	Details of aging analysis of other receivables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Neither past due nor impaired ￦ 2,971,239 ￦ 3,271,949 Past due and impaired Up to 6 months 134,231 169,894 6 months to 12 months 12,805 16,052 Over 12 months 124,152 77,054 271,188 263,000 Less: Allowance for doubtful accounts (141,616 ) (84,372 ) Total ￦ 3,100,811 ￦ 3,450,577

Other Financial Assets and Li52

Other Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Other Financial Assets and Liabilities	Details of other financial assets and liabilities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other financial assets Financial assets at fair value through profit or loss ￦ 6,277 ￦ 5,813 Derivatives used for hedge 227,318 7,389 Financial instruments 1 716,769 1,333,317 Available-for-sale financial assets 1 404,774 380,953 Held-to-maturity investments 30,143 151 Less: Non-current (664,726 ) (754,992 ) Current ￦ 720,555 ) ￦ 972,631 ) Other financial liabilities Financial liabilities at fair value through the profit or loss ￦ 1,973 ￦ 5,051 Derivatives used for hedge 14,928 93,770 Other financial liabilities 91,763 87,669 Less: Non-current (108,431 ) (149,267 ) Current ￦ 233 ￦ 37,223 1 As of December 31, 2017, MMW(Money Market Wrap) and MMT(Money Market Trust) amounting to ￦ ￦ ￦
Summary of Financial Instruments at Fair Value Through Profit or Loss	Financial instruments at fair value through profit or loss as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Assets Liabilities Assets Liabilities Financial instruments at fair value through profit and loss ￦ 6,277 ￦ — ￦ 5,813 ￦ — Other derivatives liabilities ￦ — ￦ 1,973 ￦ — ￦ 5,051
Summary of Financial Assets and Liabilities at Fair Value Through Profit or Loss	Financial instruments at fair value through profit or loss 2015 2016 2017 (in millions of Korean won) Valuation Valuation Valuation Valuation Valuation Valuation Valuation gains and losses on financial assets ￦ — ￦ — ￦ 470 ￦ 7,654 ￦ — ￦ 464 Total ￦ — ￦ — ￦ 470 ￦ 7,654 ￦ — ￦ 464
Summary of Financial Assets Held for Trading	Held for trading 2015 2016 2017 (in millions of Korean won) Valuation Valuation Valuation Valuation Valuation Valuation Valuation gains and losses on financial assets ￦ — ￦ 2,006 ￦ 33 ￦ — ￦ — ￦ 3,078 Total ￦ — ￦ 2,006 ￦ 33 ￦ — ￦ — ￦ 3,078
Summary of Derivative Financial Assets and Liabilities	Derivatives used for hedge as of December 31, 2016 and 2017, are as follows: 2016 2017 (in millions of Korean won) Assets Liabilities Assets Liabilities Interest rate swap 1 ￦ — ￦ 3,278 ￦ — ￦ 2,633 Currency swap 2 214,648 11,650 7,389 81,300 Currency forwards 3 12,670 — — 9,837 Total 227,318 14,928 7,389 93,770 Less: non-current (97,220 ) (14,695 ) (4,675 ) (56,547 ) Current ￦ 130,098 ￦ 233 ￦ 2,714 ￦ 37,223 1 The interest rate swap contract is to hedge the risk of variability in future fair value of the bond. 2 The currency swap contract is to hedge the risk of variability in cash flow from the bond. In applying the cash flow hedge accounting, the Group hedges its exposures to cash flow fluctuation until September 7, 2034. 3 The currency forward contract is to hedge the risk of variability in cash flow from transactions in foreign currencies due to changes in foreign exchange rate.
Summary of Valuation Gains and Losses on Derivatives Contracts	The valuation gains and losses on the derivatives contracts for the years ended December 31, 2015, 2016 and 2017, are as follows: (in millions of 2015 2016 2017 Type of Valuation Valuation Other comprehensive 1 Valuation Valuation Other comprehensive 1 Valuation Valuation Other comprehensive 1 Interest rate swap ￦ — ￦ — ￦ (2,858 ) ￦ — ￦ 148 ￦ (142 ) ￦ 38 ￦ — ￦ 637 Currency swap 141,512 1,733 150,255 97,158 (10 ) 85,479 19 187,468 (146,752 ) Currency forwards — — 247 12,278 — 146 — 22,114 (393 ) Total ￦ 141,512 ￦ 1,733 ￦ 147,644 ￦ 109,436 ￦ 138 ￦ 85,483 ￦ 57 ￦ 209,582 ￦ (146,508 ) 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling interest.
Summary of Available-For-Sale Financial Assets	Details of available-for-sale financial assets as of December 31, 2016, and 2017 are as follows: (In millions of Korean won) 2016 2017 Marketable equity securities ￦ 5,387 ￦ 6,859 Non-marketable equity securities 372,703 364,195 Debt securities 26,684 9,899 Total 404,774 380,953 Less: non-current (384,798 ) (379,488 ) Current ￦ 19,976 ￦ 1,465
Summary of Changes in Available-for-Sale Financial Assets	Changes of available-for-sale financial assets for the years ended December 31, 2016, and 2017 are as follows: (In millions of Korean won) 2016 2017 Beginning ￦ 360,037 ￦ 404,774 Acquisition 44,302 89,027 Disposal (18,161 ) (129,682 ) Valuation 1 14,413 67,593 Impairment (966 ) (6,137 ) Reclassification 5,149 (44,622 ) Changes in scope of consolidation — — Ending ￦ 404,774 ￦ 380,953 1 The amounts before adjustments of deferred income tax directly reflected in equity and allocation to the non-controlling interest.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Inventories Net	Inventories as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Acquisition Valuation Book Acquisition Valuation Book Merchandise ￦ 403,938 ￦ (46,634 ) ￦ 357,304 ￦ 504,321 ￦ (58,293 ) ￦ 446,028 Others 97,778 (494 ) 97,284 195,999 — 195,999 Total ￦ 501,716 ￦ (47,128 ) ￦ 454,588 ￦ 700,320 ￦ (58,293 ) ￦ 642,027

Other Assets and Liabilities (T

Other Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
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Summary of Other Assets and Liabilities	Other assets and liabilities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other assets Advance payments ￦ 148,299 ￦ 164,950 Prepaid expenses 255,464 241,078 Others 13,471 5,998 Less: Non-current (106,099 ) (107,166 ) Current ￦ 311,135 ￦ 304,860 Other liabilities Advances received ￦ 281,071 ￦ 375,792 Withholdings 89,679 85,142 Unearned revenue 24,142 23,036 Others 6,160 11,629 Less: Non-current (58,761 ) (237,284 ) Current ￦ 342,291 ￦ 258,315

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Changes in Property, Plant and Equipment	Changes in property, plant and equipment for the years ended December 31, 2016 and 2017, are as follows: 2016 (in millions of Korean won) Land Buildings Machinery Others Construction- Total Acquisition cost ￦ 1,287,749 ￦ 3,558,460 ￦ 34,388,584 ￦ 1,951,749 ￦ 1,033,777 ￦ 42,220,319 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,459,416 ) (24,879,791 ) (1,400,766 ) (1,300 ) (27,741,405 ) Beginning, net 1,287,617 2,099,044 9,508,793 550,983 1,032,477 14,478,914 Acquisition 291 3,608 247,431 146,471 2,297,346 2,695,147 Disposal/Abandonment (855 ) (1,650 ) (112,135 ) (8,155 ) (3,357 ) (126,152 ) Depreciation — (135,389 ) (2,498,837 ) (143,978 ) — (2,778,204 ) Impairment — — 361 (47,086 ) — (46,725 ) Transfer in (out) 4,274 136,041 2,060,936 11,073 (2,212,324 ) — Inclusion in scope of consolidation — — 68 764 — 832 Others 17,625 23,078 53,568 14,851 (20,823 ) 88,299 Ending, net ￦ 1,308,952 ￦ 2,124,732 ￦ 9,260,185 ￦ 524,923 ￦ 1,093,319 ￦ 14,312,111 Acquisition cost ￦ 1,309,084 ￦ 3,729,228 ￦ 35,106,184 ￦ 1,895,332 ￦ 1,093,941 ￦ 43,133,769 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,604,496 ) (25,845,999 ) (1,370,409 ) (622 ) (28,821,658 ) 2017 (In millions of Korean won) Land Buildings Machinery Others Construction- Total Acquisition cost ￦ 1,309,084 ￦ 3,729,228 ￦ 35,106,184 ￦ 1,895,332 ￦ 1,093,941 ￦ 43,133,769 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,604,496 ) (25,845,999 ) (1,370,409 ) (622 ) (28,821,658 ) Beginning, net 1,308,952 2,124,732 9,260,185 524,923 1,093,319 14,312,111 Acquisition 1,948 120 237,218 129,464 2,262,681 2,631,431 Disposal and termination (4,656 ) (4,022 ) (176,085 ) (8,242 ) (3,133 ) (196,138 ) Depreciation — (135,242 ) (2,469,459 ) (150,535 ) — (2,755,236 ) Impairment (Recovery of impairment) — — (9,256 ) (1 ) (28 ) (9,285 ) Transfer in (out) 26,764 25,305 2,227,808 10,344 (2,600,908 ) (310,687 ) Exclusion from scope of consolidation — (19 ) (772 ) (120 ) (34 ) (945 ) Transfer from(to) investment properties (64,449 ) 1,793 — 1,184 — (61,472 ) Others 98 (245 ) (8,830 ) (179 ) (38,304 ) (47,460 ) Ending, net ￦ 1,268,657 ￦ 2,012,422 ￦ 9,060,809 ￦ 506,838 ￦ 713,593 ￦ 13,562,319 Acquisition cost ￦ 1,268,789 ￦ 3,750,861 ￦ 35,971,877 ￦ 1,920,571 ￦ 714,706 ￦ 43,626,804 Less: Accumulated depreciation (including accumulated impairment loss and others) (132 ) (1,738,439 ) (26,911,068 ) (1,413,733 ) (1,113 ) (30,064,485 )
Summary of the Details of Property, Plant and Equipment Provided	Details of property, plant and equipment provided as collateral as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Carrying Secured Related line item Related Secured party Land and Buildings ￦ 13,337 ￦ 16,009 Borrowings ￦ 11,540 Standard Korea Others 55,951 43,506 25,379 Shinhan Bank (In millions of Korean won) 2017 Carrying Secured Related line item Related Secured party Land and Buildings 13,115 15,995 Borrowings 2,730 Standard Korea Others 53,757 38,570 16,071 Shinhan Bank

Investment Properties (Tables)

Investment Properties (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Investment Properties	Changes in investment properties for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Land Buildings Construction-in- Total Acquisition cost ￦ 340,790 ￦ 1,011,236 ￦ 74,208 ￦ 1,426,234 Less: Accumulated depreciation — (324,164 ) — (324,164 ) Beginning 340,790 687,072 74,208 1,102,070 Acquisition 51 417 160,138 160,606 Disposal/Abandonment (5,837 ) (1,802 ) — (7,639 ) Depreciation — (43,575 ) — (43,575 ) Transfer (32,254 ) 124,417 (155,581 ) (63,418 ) Ending ￦ 302,750 ￦ 766,529 ￦ 78,765 ￦ 1,148,044 Acquisition cost ￦ 302,750 ￦ 1,119,885 ￦ 78,765 ￦ 1,501,400 Less: Accumulated depreciation — ￦ (353,356 ) — ￦ (353,356 ) (In millions of Korean won) 2017 Land Buildings Construction-in- progress Total Acquisition cost ￦ 302,750 ￦ 1,119,885 ￦ 78,765 ￦ 1,501,400 Less: Accumulated depreciation — (353,356 ) — (353,356 ) Beginning 302,750 766,529 78,765 1,148,044 Acquisition — 775 48,075 48,850 Disposal/Abandonment (3,493 ) (6,434 ) — (9,927 ) Depreciation — (47,295 ) — (47,295 ) Transfer from(to) property, plant and equipment 64,449 (1,793 ) (1,184 ) 61,472 Transfer and others (6,916 ) 80,986 (85,683 ) (11,613 ) Ending ￦ 356,790 ￦ 792,768 ￦ 39,973 ￦ 1,189,531 Acquisition cost ￦ 358,358 ￦ 1,191,687 ￦ 39,973 ￦ 1,590,018 Less: Accumulated depreciation (include. Accumulated impairment) (1,568 ) (398,919 ) — (400,487 )
Summary of Investment Properties Provided as Collateral	Details of investment properties provided as collateral as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Carrying Secured Related Related Buildings ￦ 711,989 ￦ 98,543 Deposits ￦ 84,334 Land and Buildings ￦ 8,035 ￦ 7,891 Borrowings ￦ 5,260 (In millions of Korean won) 2017 Carrying Secured Related Related Buildings ￦ 772,708 ￦ 104,861 Deposits ￦ 90,150 Land and Buildings ￦ 7,897 ￦ 7,905 Borrowings ￦ 5,270

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Intangible Assets	Changes in intangible assets for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Goodwill Development 1 Software Frequency usage rights Others Total Acquisition cost 449,379 1,487,420 805,387 2,591,229 1,109,085 6,442,500 Less: Accumulated amortization (including accumulated impairment loss and others) (107,038 ) (1,025,877 ) (574,003 ) (1,618,459 ) (517,372 ) (3,842,749 ) Beginning, net ￦ 342,341 ￦ 461,543 ￦ 231,384 ￦ 972,770 ￦ 591,713 ￦ 2,599,751 Acquisition and capital expenditure — 36,075 35,631 978,309 74,312 1,124,327 Disposal and termination — (8,600 ) (1,928 ) — (16,397 ) (26,925 ) Amortization — (162,682 ) (78,643 ) (273,790 ) (84,606 ) (599,721 ) Impairment (131,600 ) — (46 ) — (3,618 ) (135,264 ) Inclusion in scope of consolidation 42,745 — 2,462 — 16,015 61,222 Others — 8,340 8,278 — (17,205 ) (587 ) Ending, net ￦ 253,486 ￦ 334,676 ￦ 197,138 ￦ 1,677,289 ￦ 560,214 ￦ 3,022,803 Acquisition cost 492,105 1,483,205 838,532 2,531,654 1,154,993 6,500,489 (238,619 ) (1,148,529 ) (641,394 ) (854,365 ) (594,779 ) (3,477,686 ) 2017 (In millions of Korean won) Goodwill Development 1 Software Frequency usage rights Others Total Acquisition cost 492,105 1,483,205 838,532 2,531,654 1,154,993 6,500,489 Less: Accumulated amortization (including accumulated impairment loss and others) (238,619 ) (1,148,529 ) (641,394 ) (854,365 ) (594,779 ) (3,477,686 ) Beginning, net ￦ 253,486 ￦ 334,676 ￦ 197,138 ￦ 1,677,289 ￦ 560,214 ￦ 3,022,803 Acquisition and capital expenditure — 247,863 60,475 — 78,373 386,711 Disposal and termination — (14,806 ) (548 ) — (11,859 ) (27,213 ) Amortization — (151,718 ) (73,174 ) (311,146 ) (99,112 ) (635,150 ) Impairment (84,606 ) — (3 ) — (31,486 ) (116,095 ) Inclusion in scope of consolidation — (332 ) (3,216 ) — (1,374 ) (4,922 ) Others — 2,876 9,569 (1,201 ) (4,674 ) 6,570 Ending, net ￦ 168,880 ￦ 418,559 ￦ 190,241 ￦ 1,364,942 ￦ 490,081 ￦ 2,632,704 Acquisition cost 474,908 1,643,886 893,500 2,530,341 1,171,378 6,714,014 Less; Accumulated amortization (including accumulated impairment loss and others) (306,028 ) (1,225,327 ) (703,259 ) (1,165,399 ) (681,297 ) (4,081,310 ) 1 The Company’s development costs mainly consist of acquisition costs to develop a combined billing system and an information management system.
Summary of Goodwill Allocated to Each Cash-Generation Unit	Goodwill is allocated to the Group’s cash-generating unit which is identified by operating segments. As of December 31, 2017, goodwill allocated to each cash-generation unit is as follows: (In millions of Korean won) Cash generating Unit Amount Marketing/Customer Telecom Wireless business 1 ￦ 65,057 Finance and Rental BC Card Co., Ltd. 2 41,234 Others PlayD Co., Ltd. (N search Marketing Co., Ltd) 3 42,745 Genie Music Corporation (KT Music Corporation) and others 19,844 Total ￦ 168,880 1 The recoverable amounts of mobile business are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 0.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate -2.46% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 8.95% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on mobile business for the years ended December 31, 2017 and 2016. 2 The recoverable amounts of BC Card Co., Ltd. are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 0.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate 0.11% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 14.62% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on BC Card Co., Ltd. for the years ended December 31, 2017 and 2016. 3 The recoverable amounts of PlayD Co., Ltd. (N search Marketing Co., Ltd.) are calculated based on value-in use calculations. These calculations use cash flow projections for the next five years based on financial budgets. An annual growth rate of 1.0% was applied for the cash flows expected to be incurred after five year. This growth rate does not exceed the long-term average growth rate of the industry which the cash-generate unit belongs in. The Group estimated its revenue growth rate 4.27% based on past performance and its expectation of future market changes. In addition, management estimated the cash flow based on past performance and its expectation of market growth, and the discount rates 9.5% used reflected specific risks relating to the relevant CGUs. As a result of the impairment test, the Group concluded that the carrying amount of CGUs does not exceed the recoverable amount. Accordingly, the Group did not recognise the impairment loss on goodwill on PlayD Co., Ltd. (N search Marketing Co., Ltd.) for the years ended December 31, 2017 and 2016.

Investments in Associates and58

Investments in Associates and Joint Ventures (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Details of Associates	Details of associates as of December 31, 2017, are as follows: Percentage of ownership (%) Location Date of 2016 2017 Korea Information & Technology Fund 33.3 % 33.3 % Korea 31-Dec KT-SB Venture Investment 1 50.0 % 50.0 % Korea 31-Dec Mongolian Telecommunications 1 40.0 % — Mongolia 31-Dec KT Wibro Infra Co., Ltd. 26.2 % — Korea 31-Dec KT-IBKC Future Investment Fund 1 1 50.0 % 50.0 % Korea 31-Dec KT-CKP New Media Investment Fund 49.7 % 49.7 % Korea 31-Dec K Bank Inc. 1 — 10.0 % Korea 31-Dec 1 At the end of the reporting period, even though the Group (KT-SB Venture Investment Fund and KT-IBKC Future Investment Fund 1) has 50% ownership, the equity method of accounting has been applied as the Group, which is a limited partner of investment fund, cannot participate in determining the operating and financial policies. As of December 31, 2017, the entire shares of Mongolian Telecommunications is classified as assets held for sale, and KT Wibro Infra Co., Ltd. was liquidated during 2017. Also, 8% of non-voting convertible stock are excluded from percentage of ownership for K bank Inc.
Summary of Changes in Investments in Associates and Joint Ventures	Changes in investments in associates and joint ventures for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Beginning Acquisition Share of net profit 1 Impairment Others Ending Korea Information & Technology Fund ￦ 127,583 ￦ — ￦ 7,446 ￦ — ￦ (60 ) ￦ 134,969 KT-SB Venture Investment 4,861 — (125 ) — — 4,736 Mongolian Telecommunications 7,483 — 32 — (1,271 ) 6,244 KT Wibro Infra Co., Ltd. 69,328 — — (17,128 ) — 52,200 KT-CKP New Media Investment Fund 3,860 — 594 — — 4,454 Others 56,914 29,052 (5,400 ) — 906 81,472 ￦ 270,029 ￦ 29,052 ￦ 2,547 ￦ (17,128 ) ￦ (425 ) ￦ 284,075 2017 (In millions of Korean won) Beginning Acquisition Share of net profit 1 Impairment Others Ending Korea Information & Technology Fund ￦ 134,969 ￦ — ￦ 4,275 ￦ — ￦ 290 ￦ 139,534 KT-SB Venture Investment 4,736 (1,069 ) (725 ) — — 2,942 Mongolian Telecommunications 6,244 — (348 ) — (5,896 ) — KT Wibro Infra Co., Ltd. 52,200 (52,200 ) — — — — KT-IBKC Future Investment Fund 1 3,621 7,500 (296 ) — — 10,825 KT-CKP New Media Investment Fund 4,454 (2,970 ) 810 — — 2,294 K Bank Inc. — 26,543 (17,244 ) — 32,809 42,108 Others 77,851 3,178 (1,952 ) (3,662 ) 6,313 81,728 ￦ 284,075 ￦ (19,018 ) ￦ (15,480 ) ￦ (3,662 ) ￦ 33,516 ￦ 279,431 1 KT investment Co., Ltd., a subsidiary of the Group, recognized its share in net profit from associates and joint ventures as operating revenue and expense. These include its share in gain from associates and joint ventures of ￦ ￦
Summary of Financial Information of Associates and Joint Ventures	Summarized financial information of associates and joint ventures as of and for the years ended December 31, 2016 and 2017, is as follows: (In millions of Korean won) 2016 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 154,651 ￦ 250,257 ￦ — ￦ — KT-SB Venture Investment 1,009 8,704 242 — Mongolian Telecommunications 9,852 9,055 3,296 — KT Wibro Infra Co., Ltd. 274,811 6 4,996 52 KT-CKP New Media Investment Fund 1,801 7,170 4 — (In millions of Korean won) 2016 Operating Profit (loss) Other Total Dividend Korea Information & Technology Fund ￦ 26,942 ￦ 22,338 ￦ (9,425 ) ￦ 12,913 ￦ 3,201 KT-SB Venture Investment 2 (251 ) — (251 ) — Mongolian Telecommunications 10,336 81 3,178 3,259 — KT Wibro Infra Co., Ltd. 391 5,025 — 5,025 — KT-CKP New Media Investment Fund 1,684 1,195 — 1,195 — (In millions of Korean won) 2017 Current Non-current assets Current Non-current liabilities Korea Information & Technology Fund ￦ 144,874 ￦ 273,727 ￦ — ￦ — KT-SB Venture Investment 120 5,770 6 — KT-IBKC Future Investment Fund 1 5,499 16,302 152 — KT-CKP New Media Investment Fund 287 4,333 — — K Bank Inc. 1,258,969 92,137 1,116,154 1,177 (In millions of Korean won) 2017 Operating Profit (loss) Other Total Dividend Korea Information & Technology Fund ￦ 36,462 ￦ 12,825 ￦ 1,868 ￦ 14,693 ￦ 739 KT-SB Venture Investment 3 (1,449 ) — (1,449 ) — KT-IBKC Future Investment Fund 1 15 (593 ) — (593 ) — KT-CKP New Media Investment Fund 1,593 1,632 — 1,632 — K Bank Inc. 20,926 (83,787 ) (746 ) (84,533 ) —
Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures	Details of a reconciliation of the summarized financial information to the carrying amount of interests in the associates and joint ventures as of and for the years end December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Net assets Percentage of Share in net Intercompany Carrying Korea Information & Technology Fund ￦ 404,908 33.3 % ￦ 134,969 ￦ — ￦ 134,969 KT-SB Venture Investment 9,471 50.0 % 4,736 — 4,736 Mongolian Telecommunications 15,610 40.0 % 6,244 — 6,244 KT Wibro Infra Co., Ltd. 269,769 26.2 % 70,679 (18,479 ) 52,200 KT-CKP New Media Investment Fund 8,967 49.7 % 4,454 — 4,454 2017 (In millions of Korean won) Net assets Percentage of Share in net Intercompany Carrying Korea Information & Technology Fund ￦ 418,601 33.3 % ￦ 139,534 ￦ — ￦ 139,534 KT-SB Venture Investment 5,884 50.0 % 2,942 — 2,942 KT-IBKC Future Investment Fund 1 21,649 50.0 % 10,825 — 10,825 KT-CKP New Media Investment Fund 4,620 49.7 % 2,294 — 2,294 K Bank Inc. 1 233,775 10.0 % 42,108 — 42,108 1 8% of non-voting convertible stock are excluded from percentage of ownership for K bank Inc

Trade and other payables (Table

Trade and other payables (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Trade and Other Payables	Details of trade and other payables as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) December 31, 2016 December 31, 2017 Current liabilities Trade payables ￦ 1,235,955 ￦ 1,399,287 Other payables 5,903,816 6,024,847 Total ￦ 7,139,771 ￦ 7,424,134 Non-current liabilities Trade payables ￦ 8,041 ￦ 4,787 Other payables 1,180,270 996,582 Total ￦ 1,188,311 ￦ 1,001,369
Summary of Other Payables	Details of other payables as of December 31, 2016 and 2017 are as follows: (In millions of Korean won) 2016 2017 Non-trade payables 1 ￦ 4,803,642 ￦ 4,773,223 Accrued expenses 1,061,002 1,011,089 Operating deposits 861,739 850,999 Others 357,703 386,118 Less: non-current (1,180,270 ) (996,582 ) Current ￦ 5,903,816 ￦ 6,024,847 1 Settlement payables of BC Card Co., Ltd. of ￦ ￦

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Borrowings	Details of borrowings as of December 31, 2016 and 2017, are as follows: Debentures (In millions of Korean won and thousands of foreign currencies) 2016 2017 Type Maturity Annual interest Foreign currency Korean won Foreign currency Korean won MTNP notes 1 Sept. 07, 2034 6.50% USD 100,000 ￦ 120,850 USD 100,000 ￦ 107,140 MTNP notes Jan. 20, 2017 — USD 350,000 422,975 — — FR notes 2 Aug. 28, 2018 LIBOR(3M)+1.15% USD 300,000 362,550 USD 300,000 321,420 MTNP notes Apr. 22, 2017 — USD 650,000 785,525 — — MTNP notes Apr. 22, 2019 2.63% USD 350,000 422,975 USD 350,000 374,990 MTNP notes Jan. 29, 2018 0.86% JPY 6,800,000 70,503 JPY 6,800,000 64,539 MTNP notes Feb. 23, 2018 0.48% JPY 15,000,000 155,522 JPY 15,000,000 142,367 MTNP notes July 18, 2026 2.50% USD 400,000 483,400 USD 400,000 428,560 MTNP notes Aug 07, 2022 2.63% — — USD 400,000 428,560 The 173-2nd Public bond Aug. 06, 2018 6.62% — 100,000 — 100,000 The 177-3rd Public bond Feb. 09, 2017 — — 170,000 — — The 179th Public bond Mar. 29, 2018 4.47% — 260,000 — 260,000 The 180-2nd Public bond Apr. 26, 2021 4.71% — 380,000 — 380,000 The 181-2nd Public bond Aug. 26, 2018 3.99% — 90,000 — 90,000 The 181-3rd Public bond Aug. 26, 2021 4.09% — 250,000 — 250,000 The 182-2nd Public bond Oct. 28, 2021 4.31% — 100,000 — 100,000 The 183-2nd Public bond Dec. 22, 2021 4.09% — 90,000 — 90,000 The 183-3rd Public bond Dec. 22, 2031 4.27% — 160,000 — 160,000 The 184-1st Public bond Apr. 10, 2018 2.74% — 120,000 — 120,000 The 184-2nd Public bond Apr. 10, 2023 2.95% — 190,000 — 190,000 The 184-3rd Public bond Apr. 10, 2033 3.17% — 100,000 — 100,000 The 185-1st Public bond Sept. 16, 2018 3.46% — 200,000 — 200,000 The 185-2nd Public bond Sept. 16, 2020 3.65% — 300,000 — 300,000 The 186-1st Public bond June 26, 2017 — — 120,000 — — The 186-2nd Public bond June 26, 2019 3.08% — 170,000 — 170,000 The 186-3rd Public bond June 26, 2024 3.42% — 110,000 — 110,000 The 186-4th Public bond June 26, 2034 3.70% — 100,000 — 100,000 The 187-1st Public bond Sept. 02, 2017 — — 110,000 — — The 187-2nd Public bond Sept. 02, 2019 2.97% — 220,000 — 220,000 The 187-3rd Public bond Sept. 02, 2024 3.31% — 170,000 — 170,000 The 187-4th Public bond Sept. 02, 2034 3.55% — 100,000 — 100,000 The 188-1st Public bond Jan. 29, 2020 2.26% — 160,000 — 160,000 The 188-2nd Public bond Jan. 29, 2025 2.45% — 240,000 — 240,000 The 188-3rd Public bond Jan. 29, 2035 2.71% — 50,000 — 50,000 The 189-1st Public bond Jan. 27, 2019 1.76% — 100,000 — 100,000 The 189-2nd Public bond Jan. 27, 2021 1.95% — 130,000 — 130,000 The 189-3rd Public bond Jan. 27, 2026 2.20% — 100,000 — 100,000 The 189-4rd Public bond Jan. 27, 2036 2.35% — 70,000 — 70,000 The 17th unsecured bond Apr. 22, 2018 1.89% — 60,000 — 60,000 7,344,300 5,987,576 Less: Current portion (1,607,570 ) (1,357,776 ) Discount on bonds (20,852 ) (19,347 ) Total ￦ 5,715,878 ￦ 4,610,453 1 As of December 31, 2017, the Controlling Company has outstanding notes in the amount of USD 100 million with fixed interest rates under Medium Term Note Program (“MTNP”) registered in the Singapore Stock Exchange, which allowed issuance of notes of up to USD 2,000 million. However, the MTN Program has been suspended since 2007. 2 Libor (3M) are approximately 1.695 % as of December 31, 2017.
Summary of Short-term Borrowings	Short-term borrowings (In millions of Korean won) 2016 2017 Type Financial institution Annual interest rates Operational Shinhan Bank 2.99% ~ 4.41% ￦ 120,300 ￦ 113,300 Standard Charted Bank — 8,000 — Korea Development Bank 3.97% 20,800 12,000 Indutrial Bank of Korea — 1,000 — SooHyup Bank 4.22% 3,000 3,000 Total ￦ 153,100 ￦ 128,300
Summary of Long-term Borrowings	Long-term borrowings (In millions of Korean won and thousands of foreign currencies) 2016 2017 Financial institution Type Annual interest rates Foreign currency Korean won Foreign currency Korean won Export-Import Bank of Korea Inter-Korean Cooperation Fund 1 1.50% — ￦ 5,181 — ￦ 4,688 Shinhan Bank General loans 2.50% — 31,000 — 30,000 Facility loans 2.56% — 6,493 — 6,000 Vessel facility loans 2 LIBOR(3M)+0.706% USD 21,000 25,379 USD 15,000 16,071 KEB Hana Bank General loans 3.95% — 3,000 — 3,000 Standard Charted Bank General loans 3.16% — — — 8,000 Woori Bank General loans — — 13,000 — — NongHyup Bank General loans 2.86% — — — 8,000 Facility loans 2.00% 123 — 123 Korea Development Bank General loans 3.27% — 30,000 — 30,000 Kookmin Bank Facility loans 2.59% — 7,000 — 2,333 NH Investment & Security Co., Ltd. Commercial papers 3.17% — 300,000 — 300,000 Others Redeemable convertible preferred stock 3 — — 950 — 950 Kookmin Bank and other 2 3.15% USD 183,796 222,117 USD 166,108 177,968 ￦ 644,243 ￦ 587,133 Less: Current portion ￦ (59,331 ) ￦ (87,398 ) Total ￦ 584,912 ￦ 499,735 1 The Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period. 2 LIBOR(3M) is approximately 1.695% as of December 31, 2017. 3 Skylife TV Co., Ltd., a subsidiary of the Group, issued 1,900,000 of redeemable convertible preferred stock with a par value per share of ￦
Summary of Repayment of Borrowings Including the Current Liabilities	Repayment schedule of the Group’s borrowings including the portion of current liabilities as of December 31, 2017, is as follows: (in millions of Korean won) Debentures Borrowings Total In local In foreign Sub- total In local In foreign Sub- total Jan 1, 2018 ~ Dec 31, 2018 ￦ 830,000 ￦ 528,326 ￦ 1,358,326 ￦ 167,395 ￦ 48,303 ￦ 215,698 ￦ 1,574,024 Jan 1, 2019 ~ Dec 31, 2019 490,000 374,990 864,990 343,465 48,303 391,768 1,256,758 Jan 1, 2020 ~ Dec 31, 2020 460,000 — 460,000 1,518 45,089 46,607 506,607 Jan 1, 2021 ~ Dec 31, 2021 950,000 — 950,000 1,518 41,875 43,393 993,393 After 2022 1,390,000 964,260 2,354,260 7,498 10,469 17,967 2,372,227 ￦ 4,120,000 ￦ 1,867,576 ￦ 5,987,576 ￦ 521,394 ￦ 194,039 ￦ 715,433 ￦ 6,703,009
Summary of Carrying Amount and Fair Value of Debentures and Borrowings	Carrying amount and fair value of the Group’s debentures and borrowings as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Type Carrying Amount Fair Value Carrying Amount Fair Value Debentures ￦ 7,323,448 ￦ 7,387,085 ￦ 5,968,229 ￦ 6,022,551 Long-term borrowings (Including current portion of long-term borrowings) 644,243 644,010 587,133 587,475 Short-term borrowings 153,100 153,100 128,300 128,300 Total ￦ 8,120,791 ￦ 8,184,195 ￦ 6,683,662 ￦ 6,738,326

Provisions (Tables)

Provisions (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Changes in Provisions	Changes in provisions for the years ended December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 17,524 ￦ 91,827 ￦ 85,921 ￦ 195,272 Increase (transfer) 3,392 13,653 40,293 57,338 Usage (640 ) (3,378 ) (37,378 ) (41,396 ) Reversal (1,238 ) (790 ) (12,007 ) (14,035 ) Ending balance ￦ 19,038 ￦ 101,312 ￦ 76,829 ￦ 197,179 Current 18,988 2,334 75,163 96,485 Non-current 50 98,978 1,666 100,694 2017 (In millions of Korean won) Litigation Restoration cost Others Total Beginning balance ￦ 19,038 ￦ 101,312 ￦ 76,829 ￦ 197,179 Increase (Transfer) 3,842 2,827 41,550 48,219 Usage (1,740 ) (2,178 ) (22,382 ) (26,300 ) Reversal (2,834 ) (1,723 ) (11,467 ) (16,024 ) Change in scope of consolidation — (22 ) (22 ) (44 ) Ending balance ￦ 18,306 ￦ 100,216, ￦ 84,508 ￦ 203,030 Current 17,238 1,766 59,168 78,172 Non-current 1,068 98,450 25,340 124,858

Net Defined Benefit Liabiliti62

Net Defined Benefit Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Amount Recognized in the Statements of Financial Position	The amounts recognized in the statements of financial position are determined as follows: (in millions of Korean won) 2016 2017 Present value of defined benefit obligations ￦ 1,713,184 ￦ 1,911,166 Fair value of plan assets (1,334,780 ) (1,519,779 ) Liabilities ￦ 378,404 ￦ 396,079 Assets in the statement of financial position ￦ — ￦ 3,692
Summary of Changes in the Defined Benefit Obligations	Changes in the defined benefit obligations for the years ended December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Beginning ￦ 1,601,974 ￦ 1,713,184 Current service cost 205,114 210,336 Interest expense 37,378 38,994 Benefit paid (127,581 ) (154,600 ) Changes due to settlements of plan (424 ) (61 ) Remeasurements: Actuarial gains and losses arising from changes in demographic assumptions (53,407 ) 3,353 Actuarial gains and losses arising from changes in financial assumptions 26,717 36,946 Actuarial gains and losses arising from experience adjustments 18,809 63,583 Changes in scope of Consolidation 4,604 (569 ) Ending ￦ 1,713,184 ￦ 1,911,166
Summary of Changes in the Fair Value of Plan Assets	Changes in the fair value of plan assets for the years ended December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Beginning ￦ 1,077,891 ￦ 1,334,780 Interest income 25,237 30,303 Remeasurements: Return on plan assets (excluding amounts included in interest income) (2,323 ) (5,557 ) Benefits paid (88,876 ) (130,510 ) Employer contributions 322,851 290,895 Changes in scope of consolidation — (132 ) Ending ￦ 1,334,780 ￦ 1,519,779
Summary of Amounts Recognized in the Statement of Profit or Loss	Amounts recognized in the statement of profit or loss for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Current service cost ￦ 200,994 ￦ 205,114 ￦ 210,336 Net Interest cost 16,793 12,141 8,691 Past service cost — 424 (61 ) Transfer out (11,942 ) (8,737 ) (9,196 ) Transfer to discontinued operation (3,031 ) — — Total expenses ￦ 202,814 ￦ 208,942 ￦ 209,770
Summary of Principal Actuarial Assumptions	Principal actuarial assumptions used are as follows: 2015.12.31 2016.12.31 2017.12.31 Discount rate 2.43 % 2.43 % 2.76 % Future salary increase 4.06 % 4.10 % 4.51 %
Summary of Expected Maturity Analysis of Undiscounted Pension Benefits	The expected maturity analysis of undiscounted pension benefits as at December 31, 2017, is as follows: (in millions of Korean won) Less than 1 year Between 1-2 Between 2-5 Over 5 years Total Pension benefits ￦ 142,963 ￦ 179,612 ￦ 627,302 ￦ 3,763,601 ￦ 4,713,478
Defined benefit obligations [Member]
Summary of Sensitivity of the Defined Benefit Obligations	The sensitivity of the defined benefit obligations as of December 31, 2017, to changes in the principal assumptions is: (in percentage, in millions of Korean won ) Effect on defined benefit obligation Changes in Increase in Decrease in Discount rate 0.5% point ￦ (62,000 ) ￦ 76,560 Salary growth rate 0.5% point 71,273 (57,848 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary Of Major Commitments With Local Financial Institutions	As of December 31, 2017, major commitments with local financial institutions are as follows: (In millions of Korean won and foreign currencies in thousands) Financial institution Currency Limit Used amount Bank overdraft Kookmin Bank and others KRW 1,730,000 72 Commercial papers NH Investment & Securities KRW 370,000 300,000 Collateralized loan on accounts receivable-trade NongHyup Bank and others KRW 35,560 — Collateralized loan on electronic accounts receivable-trade Shinhan Bank and others KRW 343,000 42,350 Plus electronic notes payable Industrial Bank of Korea KRW 50,000 140 Loans for working capital Korea Development Bank KRW 306,500 207,300 Green energy factoring Shinhan Bank KRW 16 16 FX forward trading commitment Shinhan Bank USD 11,500 — Facility loans Kookmin Bank and others KRW 8,456 8,456 USD 212,000 166,108 Facility loans on ships Shinhan Bank USD 30,000 15,000 Inter-Korean Cooperation Fund Export-Import Bank of Korea KRW 37,700 4,688 Total KRW 2,881,232 563,022 USD 253,500 181,108
Summary of Guarantees Received from Financial Institutions	As of December 31, 2017, guarantees received from financial institutions are as follows: (In millions of Korean won and thousands of foreign currencies) Financial institution Currency Limit Performance guarantee Seoul Guarantee Insurance and others KRW 116,787 USD 1,275 Guarantee for import letters of credit Industrial Bank of Korea and others USD 5,980 Guarantee for payment in foreign currency KEB Hana and others USD 54,072 PLN 1 23,000 Guarantee for advances received Export-Import Bank of Korea USD 7,414 Comprehensive credit line KEB Hana Bank and others KRW 55,000 Bid guarantee KEB Hana Bank USD 400 Bid guarantee Korea Software Financial Cooperative KRW 96,911 Performance guarantee /Warranty Guarantee KRW 302,062 Guarantee for advances received/others Korea Software Financial Cooperative KRW 99,228 Warranty guarantee Seoul Guarantee Insurance KRW 2,962 Guarantees for licensing KRW 4,077 Guarantees for public sale KRW 50 Guarantees for deposits Seoul Guarantee Insurance and others KRW 4,203 Total KRW 681,280 USD 69,141 PLN 1 23,000 1 Polish Zloty.
Summary Of Guarantees Provided By The Group For Third Parties	As of December 31, 2017, guarantees provided by the Group to a third party, are as follows: (in millions of Korean won) Subject to payment guarantees Creditor Limit Used amount Period KT Estate Inc. Busan Gaya Centreville Buyers Shinhan ￦ ￦ Nov 10, 2017 ~Oct. 31, 2020 KT Estate Inc. Daegu Beomeo -Crossroads Shinhan 81,722 14,237 Oct 29, 2017 ~Nov. 30, 2020 KT Hitel Co., Ltd. KEB Hana Bank Cash 384 — Apr 19, 2017 ~ Apr 19, 2018

Lease (Tables)

Lease (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary Of Details Of Finance Lease Assets	Details of finance lease assets as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Acquisition costs ￦ 298,631 ￦ 325,975 Less: Accumulated depreciation (105,013 ) (126,091 ) Net balance ￦ 193,618 ￦ 199,884
Summary Of Details Of Future Minimum Lease Payments Under Finance Lease Contracts	Details of future minimum lease payments As of December 31, 2016 and 2017, under finance lease contracts are summarized below: (in millions of Korean won) 2016 2017 Total amount of minimum lease payments Within one year ￦ 79,644 ￦ 88,441 From one year to five years 131,813 132,113 More than five years — 81 211,457 220,635 Unrealized interest expense 30,743 43,758 Net amount of minimum lease payments Within one year 64,008 68,651 From one year to five years 116,706 108,146 More than five years — 80 Total ￦ 180,714 ￦ 176,877
Summary Of Details Of future Minimum Lease Payments Under Operating Lease Contracts	Details of future minimum lease payments As of December 31, 2016 and 2017, under operating lease contracts are summarized below: (in millions of Korean won) 2016 2017 Within one year ￦ 102,015 ￦ 109,258 From one year to five years 270,462 266,434 Thereafter 16,549 1,635 Total ￦ 389,026 ￦ 377,327

Share Capital (Tables)

Share Capital (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Share Capital	As of December 31, 2016 and 2017, the Group’s number of authorized shares is one billion. 2016 2017 Number of outstanding Par value per share (Korean won) Ordinary Shares (in millions of Korean won) Number of outstanding Par value per share (Korean won) Ordinary Shares (in millions of Korean won) Ordinary shares 1 261,111,808 ￦ 5,000 ￦ 1,564,499 261,111,808 ￦ 5,000 ￦ 1,564,499 1 The Group retired 51,787,959 treasury shares against retained earnings. Therefore, the ordinary shares amount differs from the amount resulting from multiplying the number of shares issued by ￦

Retained Earnings (Tables)

Retained Earnings (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Retained Earnings	Details of retained earnings as of December 31, 2016 and 2017, are as follows: (in millions of Korean won) 2016 2017 Legal reserve 1 ￦ 782,249 ￦ 782,249 Voluntary reserves 2 4,651,362 4,651,362 Unappropriated retained earnings 4,210,872 4,393,315 Total ￦ 9,644,483 ￦ 9,826,926 1 The Commercial Code of the Republic of Korea requires the Group to appropriate, as a legal reserve, an amount equal to a minimum of 10% of cash dividends paid until such reserve equals 50% of its issued capital stock. The reserve is not available for the payment of cash dividends, but may be transferred to capital stock with the approval of the Group’s Board of Directors or used to reduce accumulated deficit, if any, with the ratification of the Group’s majority shareholders. 2 The provision of research and development of human is separately accumulated with tax reserve fund during earned surplus disposal by Tax Reduction and Exemption Control Act of Korea. Reversal of this provision can be paid out as dividends according to related tax law.

Accumulated Other Comprehensi67

Accumulated Other Comprehensive Income and Other Components of Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Accumulated Other Comprehensive Income	As of December 31, 2016 and 2017, the details of the Controlling Company’s accumulated other comprehensive income are as follows: (in millions of Korean won) 2016 2017 Changes in investments in associates and joint ventures ￦ (10,883 ) ￦ (735 ) Loss on derivatives valuation (34,309 ) (3,463 ) Gain of valuation on available-for-sale 54,106 52,673 Foreign currency translation adjustment (10,346 ) (17,490 ) Total ￦ (1,432 ) ￦ 30,985
Summary of Changes in Accumulated Other Comprehensive Income	Changes in accumulated other comprehensive income for the years ended December 31, 2016 and 2017, are as follows: 2016 (in millions of Korean won) Beginning Increase Reclassified to Ending Changes in investments in associates and ￦ (10,312 ) ￦ (571 ) ￦ — ￦ (10,883 ) Gain or loss on derivatives valuation (23,234 ) 64,796 (75,871 ) (34,309 ) Gain or loss of valuation on available-for-sale 52,415 5,204 (3,513 ) 54,106 Foreign currency translation adjustment (4,999 ) (5,347 ) — (10,346 ) Total ￦ 13,870 ￦ 64,082 ￦ (79,384 ) ￦ (1,432 ) 2017 (in millions of Korean won) Beginning Increase Reclassified to Ending Changes in investments in associates and ￦ (10,883 ) ￦ 10,148 ￦ — ￦ (735 ) Gain or loss on derivatives valuation (34,309 ) (111,083 ) 141,929 (3,463 ) Gain or loss of valuation on available-for-sale 54,106 54,017 (55,450 ) 52,673 Foreign currency translation adjustment (10,346 ) (7,144 ) — (17,490 ) Total ￦ (1,432 ) ￦ (54,062 ) ￦ 86,479 ￦ 30,985
Summary of Other Components of Equity	As of December 31, 2016 and 2017, the other components of equity are as follows: (in millions of Korean won) 2016 2017 Treasury stock 1 ￦ (859,789 ) ￦ (853,108 ) Loss on disposal of treasury stock 2 607 873 Share-based payments 5,762 6,483 Others 3 (364,514 ) (359,550 ) Total ￦ (1,217,934 ) ￦ (1,205,302 ) 1 During the year ended December 31, 2017, the Group granted 125,412 treasury shares as share-based payment. 2 The amount directly reflected in equity is ￦ ￦ 3 Profit or loss incurred from transactions with non-controlling
Summary of Treasury Stock	As of December 31, 2016 and 2017, the details of treasury stock are as follows: 2016 2017 Number of shares 16,140,165 16,014,753 Amounts (In millions of Korean won) ￦ 859,789 ￦ 853,108

Share-based Payments (Tables)

Share-based Payments (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Details of Share-Based Payments	Details of share-based payments as of December 31, 2017, are as follows: 11th Grant date July 27, 2017 Grantee CEO, inside directors, outside directors, executives Vesting conditions Service condition: 1 year Non-market Fair value per option (in Korean won) ￦ Total compensation costs (in Korean won) ￦ Estimated exercise date (exercise date) After July 27, 2018 Valuation method Fair value method
Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price	Changes in the number of stock options and the weighted-average exercise price as of December 31, 2016 and 2017, are as follows: 2016 Beginning Granted Expired Forfeited Exercised 1 Ending Number of 9th grant ￦ 263,123 ￦ 54,913 ￦ 181,685 ￦ — ￦ 136,351 ￦ — ￦ — 10th grant — 318,506 — — — 318,506 — Total ￦ 263,123 ￦ 373,419 ￦ 181,685 ￦ — ￦ 136,351 ￦ 318,506 ￦ — 2017 Beginning Granted Expired Forfeited Exercised 1 Ending Number of 10th grant ￦ 318,506 ￦ — ￦ 193,094 ￦ — ￦ 125,412 ￦ — ￦ — 11th grant — 316,949 — — — 316,949 — Total ￦ 318,506 ￦ 316,949 ￦ 193,094 ￦ — ￦ 125,412 ￦ 316,949 ￦ — 1 The weighted average price of ordinary shares at the time of exercise during 2017 was ￦ ￦

Operating Revenues (Tables)

Operating Revenues (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Operating Revenues	Operating revenues for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Services provided ￦ 19,455,693 ￦ 19,935,865 ￦ 19,898,725 Sale of goods 2,755,980 2,819,141 3,360,816 Others 488,183 365,872 287,388 Total ￦ 22,699,856 ￦ 23,120,878 ￦ 23,546,929

Operating Expenses (Tables)

Operating Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Operating Expenses	Operating expenses for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Salaries and wages ￦ 3,303,484 ￦ 3,477,596 ￦ 3,568,456 Depreciation 2,756,131 2,762,773 2,745,969 Amortization of intangible assets 582,467 582,493 618,533 Commissions 1,036,852 1,099,429 1,085,865 Interconnection charges 689,293 690,285 640,612 International interconnection fee 231,060 216,633 214,058 Purchase of inventories 3,963,036 3,407,263 4,053,693 Changes of inventories (198,028 ) 162,323 (187,439 ) Sales commission 1,856,595 1,968,035 2,201,778 Service cost 1,163,887 1,322,337 1,428,405 Utilities 319,303 323,406 323,313 Taxes and dues 256,958 255,480 279,574 Rent 469,950 455,457 448,772 Insurance premium 211,104 178,231 69,384 Installation fee 249,413 156,669 146,783 Advertising expenses 177,348 185,560 197,114 Research and development expenses 183,821 167,881 168,635 Card service cost 2,959,765 3,049,559 3,094,894 Others 1,410,349 1,319,688 1,379,438 Total ￦ 21,622,788 ￦ 21,781,098 ￦ 22,477,837
Summary of Details of Employee Benefits	Details of employee benefits for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Short-term employee benefits ￦ 3,055,699 ￦ 3,206,904 ￦ 3,297,944 Post-employment benefits(Defined benefit plan) 202,814 208,942 209,770 Post-employment benefits(Defined contribution plan) 35,699 46,023 45,936 Post-employment benefits(Others) 5,535 8,017 6,949 Share-based payment 3,737 7,710 7,660 Total ￦ 3,303,484 ￦ 3,477,596 ￦ 3,568,259

Financial Income and Costs (Tab

Financial Income and Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Details of Financial Income	Details of financial income for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Interest income ￦ 70,035 ￦ 115,686 ￦ 93,078 Gain on foreign currency transactions 18,766 24,915 79,653 Gain on foreign currency translation 11,280 12,165 225,580 Gain on settlement of derivatives 368 8,515 — Gain on valuation of derivatives 141,512 109,436 57 Others 30,899 25,422 7,960 Total ￦ 272,860 ￦ 296,139 ￦ 406,328
Summary of Details of Financial Expense	Details of financial expenses for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Interest expenses ￦ 385,925 ￦ 337,219 ￦ 302,464 Loss on foreign currency transactions 42,831 37,936 40,303 Loss on foreign currency translation 175,613 121,949 12,239 Loss on settlement of derivatives 6,280 632 58,569 Loss on valuation of derivatives 1,733 138 209,582 Loss on disposal of trade receivables 2,539 15,838 20,355 Impairment loss on available-for-sale 1,805 966 9 Others 28,605 409 1,010 ￦ 645,331 ￦ 515,087 ￦ 644,531

Deferred Income Tax and Incom72

Deferred Income Tax and Income Tax Expense (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Analysis of Deferred Tax Assets and Deferred Tax Liabilities	The analysis of deferred tax assets and deferred tax liabilities as of December 31, 2016 and 2017, is as follows: (In millions of Korean won) 2016 2017 Deferred tax assets Deferred tax assets to be recovered within 12 months ￦ 265,997 ￦ 318,339 Deferred tax assets to be recovered after 1,124,420 1,140,252 ￦ 1,390,417 ￦ 1,458,591 Deferred tax liabilities Deferred tax liability to be recovered within 12 months (48,033 ) (15,705 ) Deferred tax liability to be recovered after (778,655 ) (859,126 ) (826,688 ) (874,831 ) Deferred tax assets after offsetting ￦ 701,409 ￦ 712,222 Deferred tax liabilities after offsetting ￦ 137,680 ￦ 128,462
Summary of Gross Movements on the Deferred Income Tax Account	The gross movements on the deferred income tax account for the years ended December 31, 2016 and 2017, are calculated as follows: (In millions of Korean won) 2016 2017 Beginning ￦ 715,747 ￦ 563,729 Charged(credited) to the statement of profit or loss (152,102 ) (1,771 ) Charged(credited) to other comprehensive income 84 21,802 Ending ￦ 563,729 ￦ 583,760
Summary of Movement in Deferred Income Tax Assets and Liabilities	The movement in deferred income tax assets and liabilities during the year, without taking into consideration the offsetting of balances within the same tax jurisdiction, is as follows: (In millions of Korean won) 2016 Beginning Statement of operations Other Ending Deferred tax liabilities Derivative instruments ￦ (19,155 ) ￦ (33,569 ) ￦ 3,536 ￦ (49,188 ) Available-for-sale (29,430 ) (10 ) (2,262 ) (31,702 ) Investment in subsidiaries, associates and joint ventures (50,235 ) (666 ) 155 (50,746 ) Depreciation (53,872 ) 14,374 — (39,498 ) Advanced depreciation provision (231,692 ) 6,005 — (225,687 ) Deposits for severance benefits (251,924 ) (55,806 ) — (307,730 ) Accrued income (1,808 ) (216 ) — (2,024 ) Reserve for technology and human resource development (1,216 ) 469 — (747 ) Others (135,802 ) 16,436 — (119,366 ) (775,134 ) (52,983 ) 1,429 (826,688 ) Deferred tax assets Provisions for impairment on trade receivables 136,743 (26,467 ) — 110,276 Inventory valuation 56 (8 ) — 48 Contribution for construction 19,618 (1,527 ) — 18,091 Accrued expenses 64,117 16,239 — 80,356 Provisions 20,353 (132 ) — 20,221 Property, plant and equipment 239,791 (6,876 ) — 232,915 Retirement benefit obligations 331,980 41,857 (1,345 ) 372,492 Withholding of facilities expenses 7,360 (450 ) — 6,910 Accrued payroll expenses 21,634 4,281 — 25,915 Deduction of installment receivables 10,513 3,374 — 13,887 Assets retirement obligation 16,974 1,112 — 18,086 Gain or loss foreign currency translation 43,283 24,418 — 67,701 Deferred revenue 43,792 (17,679 ) — 26,113 Real-estate sales 2,980 871 — 3,851 (In millions of Korean won) 2016 Beginning Statement of operations Other Ending Tax credit carryforwards 212,820 (13,221 ) — 199,599 Accumulated deficit 107,485 (107,485 ) — — Others 211,382 (17,426 ) — 193,956 1,490,881 (99,119 ) (1,345 ) 1,390,417 Net balance ￦ 715,747 ￦ (152,102 ) ￦ 84 ￦ 563,729 (In millions of Korean won) 2017 Beginning Statement operations Other Ending Deferred tax liabilities Derivative instruments ￦ (49,188 ) ￦ 49,188 ￦ — ￦ — Available-for-sale (31,702 ) (164 ) 1,346 (30,520 ) Investment in subsidiaries, associates and joint ventures (50,746 ) (42,659 ) (3,245 ) (96,650 ) Depreciation (39,498 ) 39,498 — — Advanced depreciation provision (225,687 ) (22,905 ) — (248,592 ) Deposits for severance benefits (307,730 ) (80,126 ) — (387,856 ) Accrued income (2,024 ) (126 ) — (2,150 ) Reserve for technology and human resource development (747 ) 433 — (314 ) Others (119,366 ) 10,617 — (108,749 ) (826,688 ) (46,244 ) (1,899 ) (874,831 ) Deferred tax assets Derivative instruments — 34,572 (9,848 ) 24,724 Provisions for impairment on trade receivables 110,276 11,380 — 121,656 Inventory valuation 48 (48 ) — — Contribution for construction 18,091 180 — 18,271 Accrued expenses 80,356 10,683 — 91,039 Provisions 20,221 3,858 — 24,079 Property, plant and equipment 232,915 (841 ) — 232,074 Retirement benefit obligations 372,492 67,751 26,806 467,049 Withholding of facilities expenses 6,910 472 — 7,382 Accrued payroll expenses 25,915 (10,786 ) — 15,129 Deduction of installment receivables 13,887 (13,887 ) — — Assets retirement obligation 18,086 2,750 — 20,836 Gain or loss foreign currency translation 67,701 (67,558 ) — 143 Deferred revenue 26,113 221 — 26,334 Real-estate sales 3,851 4,847 — 8,698 Tax credit carryforwards 199,599 (48,823 ) — 150,776 Deficit carried over — 2,699 — 2,699 (In millions of Korean won) 2017 Beginning Statement operations Other Ending Others 193,956 47,003 6,743 247,702 1,390,417 44,473 23,701 1,458,591 Net balance ￦ 563,729 ￦ (1,771 ) ￦ 21,802 ￦ 583,760
Summary of Tax Impacts Recognized Directly To Equity	The tax impacts recognized directly to equity as of December 31, 2015, 2016 and 2017, are as follows: 2015 2016 2017 (In millions of Korean won) Before recognition Tax After Before recognition Tax After Before recognition Tax After Available-for-sale ￦ (47,515 ) ￦ 11,499 ￦ (36,016 ) ￦ 9,347 ￦ (2,262 ) ￦ 7,085 ￦ (5,561 ) ￦ 1,346 ￦ (4,215 ) Hedge instruments valuation gain(loss) 18,406 (4,454 ) 13,952 (14,611 ) 3,536 (11,075 ) 40,694 (9,848 ) 30,846 Remeasurements from net defined benefit liabilities (49,963 ) 12,091 (37,872 ) 5,558 (1,345 ) 4,213 (110,768 ) 26,806 (83,962 ) Shares of gain(loss) of associates and joint ventures (5,297 ) 1,282 (4,015 ) (641 ) 155 (486 ) 13,410 (3,245 ) 10,165 Foreign currency translation adjustment (6,443 ) 1,559 (4,884 ) (7,133 ) 1,726 (5,407 ) (27,865 ) 6,743 (21,122 ) Total ￦ (90,812 ) ￦ 21,977 ￦ (68,835 ) ￦ (7,480 ) ￦ 1,810 ￦ (5,670 ) ￦ (90,090 ) ￦ 21,802 ￦ (68,288 )
Summary of Details of Income Tax Expense (Benefit)	Details of income tax expense(benefit) for the years ended December 31, 2015, 2016 and 2017, are calculated as follows: (In millions of Korean won) 2015 2016 2017 Current income tax expense(benefit) ￦ (5,003 ) ￦ 176,212 ￦ 268,885 Impact of change in deferred taxes 232,134 152,102 1,771 Income tax expense ￦ 227,131 ￦ 328,314 ￦ 270,656
Summary of Tax on the Group's Profit Before Tax	The tax on the Group’s profit before tax differs from the theoretical amount that would arise using the weighted average tax rate applicable to profits of the entities as follows: 2015 2016 2017 Profit before income tax expense ￦ 710,741 ￦ 1,123,431 ￦ 816,997 Statutory income tax expense ￦ 171,999 ￦ 271,870 ￦ 197,251 Tax effect Income not taxable for taxation purposes (21,881 ) (28,093 ) (19,268 ) Non-deductible expenses 28,849 21,947 39,746 Tax credit (9,660 ) (13,764 ) (27,211 ) Additional payment of income taxes 997 (4,780 ) 976 Tax effect and adjustment on consolidation Goodwill impairment 23,185 31,847 20,475 Eliminated dividend income form subsidiaries 20,452 40,087 34,305 Changes of out-side tax effect 9,844 (567 ) 17,990 Others 3,346 9,767 6,392 Income tax expense ￦ 227,131 ￦ 328,314 ￦ 270,656

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Basic and Diluted Earnings per Share From Operations	Basic earnings per share from operations for the years ended December 31, 2015, 2016 and 2017, is calculated as follows: 2015 2016 2017 Profit attributable to ordinary shares (In millions of Korean won) ￦ 546,361 ￦ 708,362 ￦ 461,559 Profit from continuing operations attributable to ordinary shares 404,045 708,362 461,559 Profit from discontinued operations attributable to ordinary shares 142,316 — — Weighted average number of ordinary shares outstanding (In number of shares) 244,854,364 244,892,313 245,017,175 Basic earnings per share (In Korean won) 2,231 2,893 1,884 Basic earnings per share from continuing operations 1,650 2,893 1,884 Basic earnings per share from discontinued operations 581 — — Diluted earnings per share from operations for the years ended December 31, 2015, 2016 and 2017 is calculated as follows: 2015 2016 2017 Profit attributable to ordinary shares (In millions of Korean won) ￦ 546,361 ￦ 708,362 ￦ 461,559 Adjusted net income attributable to ordinary shares (In millions of Korean won) (75 ) (67 ) — Diluted profit attributable to ordinary shares (In millions of Korean won) 546,286 708,295 461,559 Diluted profit from continuing operations attributable to ordinary shares 403,970 708,295 461,559 Diluted income from discontinued operations attributable to ordinary shares 142,316 — — Number of dilutive potential ordinary shares outstanding (In number of shares) 1,104 84,245 79,880 Weighted average number of ordinary shares outstanding (In number of shares) 244,855,468 244,976,558 245,097,055 Diluted earnings per share (In Korean won) 2,231 2,891 1,883 Diluted earnings per share from continuing operations 1,650 2,891 1,883 Diluted earnings per share from discontinued operations 581 — —

Cash Generated from Operations

Cash Generated from Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Cash Flows from Operating Activities	Cash flows from operating activities for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 1. Profit for the year ￦ 624,685 ￦ 795,117 ￦ 546,341 2. Adjustments to reconcile net income Income tax expense 346,146 328,314 270,656 Interest income (161,123 ) (130,066 ) (108,639 ) Interest expense 445,814 337,219 302,464 Dividends income (11,371 ) (3,926 ) (4,785 ) Depreciation 3,030,821 2,821,779 2,802,531 Amortization of intangible assets 609,185 599,721 635,150 Provision for severance benefits 217,787 217,255 218,966 Impairment losses on trade receivables 161,448 92,711 45,704 Share of net profit or loss of associates and joint ventures (5,562 ) (2,547 ) 15,480 Loss(gain) on disposal of associates and joint ventures (4,848 ) (1,450 ) 979 Impairment loss of associates and joint ventures — 17,128 3,662 Gain on disposal of subsidiaries (256,230 ) — — Loss on disposal of property, plant and equipment and investment in properties 129,466 74,913 150,293 Loss on disposal of intangible assets 33,978 7,703 4,271 Loss on impairment of intangible assets 292,345 135,264 116,095 Loss on foreign currency translation 164,374 109,784 (213,341 ) Loss(gain) on valuation of derivatives (306,538 ) (117,181 ) 268,094 Impairment losses on available-for-sale 1,805 966 9 Gain on disposal of available-for-sale (131,041 ) (22,695 ) (89,598 ) Others 24,140 64,863 (251,193 ) 3. Changes in operating assets and liabilities Decrease(increase) in trade receivables 112,674 252,196 (303,340 ) Increase in other receivables (21,749 ) (770,893 ) (346,013 ) Decrease(increase) in other current assets (19,701 ) 48,549 11,792 Increase in other non-current (137,532 ) (51,765 ) (43,790 ) Decrease(increase) in inventories (270,343 ) 167,873 (205,403 ) Increase(decrease) in trade payables 81,295 (114,838 ) 162,110 Increase(decrease) in other payables (48,680 ) 705,807 214,689 Increase(decrease) in other current liabilities (9,452 ) 37,798 288,553 Increase in other non-current 119,836 30,762 174,618 Decrease in provisions (8,902 ) (12,583 ) (12,574 ) Decrease in deferred revenue (82,582 ) (69,179 ) (13,086 ) Increase in plan assets (223,194 ) (224,244 ) (203,420 ) Payment of severance benefits (117,691 ) (121,835 ) (118,391 ) 4. Cash generated from operations (1+2+3) ￦ 4,579,260 ￦ 5,202,520 4,318,884
Summary of Significant Transactions not Affecting Cash Flows	Significant transactions not affecting cash flows for the years ended December 31, 2015, 2016 and 2017, are as follows: (In millions of Korean won) 2015 2016 2017 Reclassification of the current portion of debentures ￦ 1,551,300 ￦ 1,617,175 ￦ 1,416,066 Reclassification of construction-in-progress 2,373,023 2,212,324 2,686,591 Reclassification of accounts payable from property, plant and equipment 78,663 91,407 225,601 Reclassification of accounts payable from intangible assets (170,870 ) 668,564 (227,108 ) Reclassification of payable from defined benefit liability 1,675 5,746 36,209 Reclassification of payable from plan assets 13,717 (9,731 ) 43,035

Changes in Liabilities Arisin75

Changes in Liabilities Arising from Financing Activities (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Changes in Liabilities Arising from Financial Activities	Changes in liabilities arising from financial activities for the periods ended December 31, 2017, are as follows: (in millions of Korean 2017 Beginning Cash flows Non-cash Ending Newly Exchange Fair value Other Borrowing ￦ 8,120,791 ￦ (1,163,917 ) ￦ — ￦ (221,495 ) ￦ — ￦ (51,717 ) ￦ 6,683,662 Financial lease liabilities 180,714 (71,735 ) 68,938 — — (1,039 ) 176,878 Derivative assets 227,318 (71,370 ) — (76,552 ) 2,687 (74,694 ) 7,389 Derivative liabilities 16,901 — — 130,674 (28,015 ) (20,740 ) 98,820 Total ￦ 8,545,724 ￦ (1,307,022 ) ￦ 68,938 ￦ (167,373 ) ￦ (25,328 ) ￦ (148,190 ) ￦ 6,966,749

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Segment Information	Details of each segment for the years ended December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) Operating revenues Operating income(loss) Depreciation and Amortization Marketing/Customer ￦ 16,130,454 ￦ 816,679 ￦ 2,897,876 Finance 3,512,721 281,477 25,466 Satellite TV 668,521 97,701 95,951 All other segments 6,115,520 (99,601 ) 314,691 26,427,216 1,096,256 3,333,984 Elimination (3,727,360 ) (19,188 ) 4,614 Consolidated amount ￦ 22,699,856 ￦ 1,077,068 ￦ 3,338,598 2016 (In millions of Korean won) Operating revenues Operating income(loss) Depreciation and Amortization Marketing/Customer ￦ 16,144,415 ￦ 1,050,053 ￦ 2,870,161 Finance 3,577,549 208,566 28,868 Satellite TV 668,945 79,987 98,895 All other segments 6,308,203 40,047 339,429 26,699,112 1,378,653 3,337,353 Elimination (3,578,234 ) (38,873 ) 7,913 Consolidated amount ￦ 23,120,878 ￦ 1,339,780 ￦ 3,345,266 2017 (In millions of Korean won) Operating revenues Operating income Depreciation and Amortization Marketing/Customer ￦ 16,242,552 ￦ 1,018,593 ￦ 2,895,930 Finance 3,637,917 205,678 28,827 Satellite TV 685,822 75,373 99,216 All other segments 6,651,552 (187,090 ) 332,153 27,217,843 1,112,554 3,356,126 Elimination (3,670,914 ) (43,462 ) 8,376 Consolidated amount ￦ 23,546,929 ￦ 1,069,092 ￦ 3,364,502
Summary of Operating Revenues and Non Current Assets by Geographical Regions	Operating revenues for the year ended December 31, 2015, 2016 and 2017 and non-current (In millions of Korean won) Operating revenues Non-current 1 Location 2015 2016 2017 2016.12.31 2017.12.31 Domestic ￦ ￦ ￦ ￦ ￦ Overseas 71,078 94,623 65,226 174,648 137,914 Total ￦ ￦ ￦ ￦ ￦ 1 Non-current

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Related Parties Outstanding Balances of Receivables and Payables	Outstanding balances of receivables and payables in relations to transactions with related parties as of December 31, 2016 and 2017, are as follows: 2016 Receivables Payables (In millions of Korean won) Trade Loans Other Trade Other payables Associates and joint ventures KT Wibro Infra Co., Ltd. ￦ — ￦ — ￦ — ￦ — ￦ 43,394 K-Realty CR-REITs 882 — 33,110 — — MOS GS Co., Ltd. 9 — 1 — 1,494 MOS Daegu Co., Ltd. 1 — — — 1,082 MOS Chungcheong Co., Ltd. 6 — 1 — 2,065 MOS Gangnam Co., Ltd. 6 — 1 — 1,129 MOS GB Co., Ltd. 19 — 5 — 2,167 MOS BS Co., Ltd. 34 — 1 — 1,114 MOS Honam Co., Ltd. 2 — — — 1,289 Others 481 — 179 3 1,266 Total ￦ 1,440 ￦ — ￦ 33,298 ￦ 3 ￦ 55,000 2017 Receivables Payables (In millions of Korean won) Trade Loans Other Trade Other payables Associates and joint ventures K-Realty CR-REITs ￦ 778 ￦ — ￦ 33,800 ￦ — ￦ — MOS GS Co., Ltd. 17 — — — 392 MOS Daegu Co., Ltd. 1 — — — 1,388 MOS Chungcheong Co., Ltd. 1 — 290 — 1,827 MOS Gangnam Co., Ltd. 6 — 1 — 287 MOS GB Co., Ltd. 17 — 1 — 778 MOS BS Co., Ltd. 34 — 1 — 46 MOS Honam Co., Ltd. 2 — 1 — 384 K Bank, Inc. 1,338 — 7,994 — 296 NgeneBio 1 2,510 — — 3 Others 54 — 1,281 — 2,135 Total ￦ 2,249 ￦ 2,510 ￦ 43,369 ￦ — ￦ 7,536
Summary of Significant Transactions With Related Parties	Significant transactions with related parties for the years ended December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) Sales Purchases 2 Associates and joint ventures KT Service Bukbu 1 ￦ 2,143 ￦ 28,550 Information Technology Solution Nambu Corporation 1 2,707 24,025 Information Technology Solution Seobu Corporation 1 2,324 20,031 Information Technology Solution Busan Corporation 1 1,496 14,049 KT Service Nambu 1 1,972 21,133 Information Technology Solution Honam Corporation 1 2,050 29,538 Information Technology Solution Daegu Corporation 1 1,256 18,272 KT Wibro Infra Co., Ltd. 11 814 Smart Channel Co., Ltd. 6,545 4,722 K- CR-REITs 2,133 38,167 MOS GS Co., Ltd. 752 17,474 MOS Daegu Co., Ltd. 357 12,227 MOS Chungcheong Co., Ltd. 310 12,735 MOS Gangnam Co., Ltd. 454 15,829 MOS GB Co., Ltd. 964 21,582 MOS BS Co., Ltd. 453 15,482 MOS Honam Co., Ltd. 470 17,004 Others 4,394 13,510 Total 3 ￦ 30,791 ￦ 325,144 1 The transactions for the year ended December 31, 2015, after KT Service Bukbu Co., Ltd. and KT Service Nambu Co., Ltd. were merged and included in the consolidation scope. 2 The amount includes acquisition of property, plant and equipment, and others. 3 Operating income amounting to ￦ 2016 (In millions of Korean won) Sales Purchases 2 Associates and joint ventures KT Wibro Infra Co., Ltd. ￦ 11 ￦ 391 Smart Channel Co., Ltd. 1 766 — K- CR-REITs 1,989 37,469 MOS GS Co., Ltd. 663 17,361 MOS Daegu Co., Ltd. 291 12,220 MOS Chungcheong Co., Ltd. 408 13,469 MOS Gangnam Co., Ltd. 412 15,797 MOS GB Co., Ltd. 891 21,802 MOS BS Co., Ltd. 441 15,346 MOS Honam Co., Ltd. 418 14,389 Others 1,719 29,422 Total ￦ 8,009 ￦ 177,666 1 The transactions for the year ended December 31, 2016, before Smart Channel Co., Ltd. was included in the consolidation scope. 2 The amount includes acquisition of property, plant and equipment, and others. 2017 (In millions of Korean won) Sales Purchases 1 Associates and joint ventures K- CR-REITs ￦ 2,233 ￦ 35,532 MOS GS Co., Ltd. 704 16,946 MOS Daegu Co., Ltd. 335 8,514 MOS Chungcheong Co., Ltd. 455 15,542 MOS Gangnam Co., Ltd. 484 16,380 MOS GB Co., Ltd. 987 21,651 MOS BS Co., Ltd. 460 15,957 MOS Honam Co., Ltd. 493 14,294 K Bank, Inc. 3 29,939 59 NgeneBio 2 43 — Others 1,149 11,384 Total ￦ 37,282 ￦ 156,259 1 The amount includes acquisition of property, plant and equipment and others. 2 It is the amount after excluded from consolidation during the year. 3 The sales amount consists of providing services of IT system construction to K Bank, Inc.
Summary of Key Management Compensation	Key management compensation for the years ended December 31, 2015, 2016 and 2017, consists of: (In millions of Korean won) 2015 2016 2017 Salaries and other short-term benefits ￦ 2,455 ￦ 2,629 ￦ 2,879 Post-employment benefits 413 381 311 Stock-based compensation 997 1,237 1,331 Total ￦ 3,865 ￦ 4,247 ￦ 4,521
Summary of Fund Transactions With Related Parties	Fund transactions with related parties for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Equity Dividend Associates and joint ventures KT-DSC start-up ￦ 6,000 ￦ — PT. Mitra Transaksi Indonesia 16,626 — K-REALTY 5,500 — AI RESEARCH INSTITUTE 3,000 — KT-IBKC 3,750 — Gyeonggi-KT 1,000 — FUNDA Co., Ltd. 2,799 — K-Realty CR-REITs — 4,186 Korea Information & Technology Investment Fund — 3,201 Daiwon Broadcasting Co., Ltd. — 85 Others — 82 Total ￦ 38,675 ￦ 7,554 (In millions of Korean won) 2017 Equity Dividend Associates and joint ventures PT. Mitra Transaksi Indonesia ￦ 5,194 ￦ — KT-IBKC 7,500 — CHAMP IT Co.,Ltd. 750 — Korea Electronic Vehicle Charging Service 864 — Gyeonggi-KT 1,000 — K-REALTY — 5,392 K Bank, Inc. 26,543 — Korea Information & Technology Investment Fund — 739 MOS GS Co., Ltd. — 12 MOS Daegu Co., Ltd. — 12 MOS Chungcheong Co., Ltd. — 12 MOS Gangnam Co., Ltd. — 10 MOS GB Co., Ltd. — 15 MOS BS Co., Ltd. — 10 MOS Honam Co., Ltd. — 10 Total ￦ 41,851 ￦ 6,212

Financial Risk Management (Tabl

Financial Risk Management (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Maximum Exposure to Credit Risk	As of December 31, 2016 and 2017, maximum exposure to credit risk is as follows. (In millions of Korean won) 2016 2017 Cash equivalents(except cash on hand) ￦ 2,875,383 ￦ 1,926,620 Trade and other receivables 6,036,363 6,643,115 Other financial assets Financial assets at fair value through profit or loss 6,277 5,813 Derivative used for hedging 227,318 7,389 Time deposits and others 716,769 1,333,317 Available-for-sale 26,684 9,899 Held-to-maturity 30,143 151 Financial guarantee contracts 1 56,373 143,969 Total ￦ 9,975,310 ￦ 10,070,273 1 Total amounts guaranteed by the Group according to the guarantee contracts.
Summary of Contractual Undiscounted Cash Flows	The table below analyzes the Group’s liabilities (including interest expenses) into relevant maturity groups based on the remaining period at the date of the end of each reporting period to the contractual maturity date. These amounts are contractual undiscounted cash flows. 2016.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Trade and other payables ￦ 7,682,604 ￦ 1,121,452 ￦ 217,411 ￦ 9,021,467 Borrowings(including debentures) 2,034,524 4,834,151 2,458,749 9,327,424 Other non-derivative 233 3,272 22,917 26,422 Financial guarantee contracts 1 56,373 — — 56,373 Total ￦ 9,773,734 ￦ 5,958,875 ￦ 2,699,077 ￦ 18,431,686 2017.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Trade and other payables ￦ 7,880,906 ￦ 1,219,835 ￦ 161,497 ￦ 9,262,238 Borrowings(including debentures) 1,623,996 3,666,726 2,317,209 7,607,931 Other non-derivative 4,117 8,452 — 12,569 Financial guarantee contracts 1 26,738 — — 26,738 Total ￦ 9,535,757 ￦ 4,895,013 ￦ 2,478,706 ￦ 16,909,476 1 Total amount guaranteed by the Group according to guarantee contracts. Cash flow from financial guarantee contracts is classified as the maturity group in the earliest period when the financial guarantee contracts can be executed.
Summary of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow	2015.12.31 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 335,970 ￦ 2,138,379 ￦ 38,184 ￦ 2,512,533 Inflow 276,066 2,284,219 46,194 2,606,479 2016.12.31 (In millions of Korean won) Less than 1 year 1-5 More than Total Outflow ￦ 1,174,147 ￦ 1,176,715 ￦ 536,005 ￦ 2,886,867 Inflow 1,302,112 1,306,199 588,559 3,196,870 2017.12.31 (In millions of Korean won) Less than 1 year 1-5 More than 5 Total Outflow ￦ 638,171 ￦ 546,791 ￦ 526,633 ￦ 1,711,595 Inflow 608,270 568,976 509,558 1,686,804
Summary of Debt-to-equity Ratios	The debt-to-equity (In millions of Korean won) 2016 2017 Total liabilities ￦ 17,881,580 ￦ 16,696,309 Total equity 12,782,718 13,049,130 Debt-to-equity 140 % 128 %
Summary of Gearing Ratios	The gearing ratios as of December 31, 2016 and 2017, are as follows: (In millions of Korean won, %) 2016 2017 Total borrowings ￦ 8,301,505 ￦ 6,860,539 Less: cash and cash equivalents (2,900,311 ) (1,928,182 ) Net debt 5,401,194 4,932,357 Total equity 12,782,718 13,049,130 Total capital 18,183,912 17,981,487 Gearing ratio 30 % 27 %
Summary of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements	Details of the Group’s recognized financial assets subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) 2016 Gross Gross Net amounts position Amounts not offset Net Financial Cash Derivative assets for hedging purpose 1 ￦ 35,334 ￦ — ￦ 35,334 ￦ (5,707 ) ￦ — ￦ 29,627 Trade receivables 2 95,865 — 95,865 (91,662 ) — 4,203 ￦ 131,199 ￦ — ￦ 131,199 ￦ (97,369 ) ￦ — ￦ 33,830 (In millions of Korean won) 2017 Gross Gross Net amounts position Amounts not offset Net Financial Cash Derivative assets for hedging purpose 1 ￦ 3,284 ￦ — ￦ 3,284 ￦ (3,284 ) ￦ — ￦ — Trade receivables 2 85,755 (5,010 ) 80,745 (73,109 ) — 7,636 Other financial assets 8,680 (436 ) 8,244 (5,307 ) — 2,937 ￦ 97,719 ￦ (5,446 ) ￦ 92,273 ￦ (81,700 ) ￦ — ￦ 10,573 1 The amount applied with master netting arrangements under the standard contract of International Swap and Derivatives Association (ISDA). 2 The amount applied with netting arrangements under the reference offer of the telecommunication facility interconnection and sharing data among telecommunications companies.
Summary of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements	The Group’s recognized financial liabilities subject to enforceable master netting arrangements or similar agreements are as follows: (In millions of Korean won) 2016 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Derivative liabilities for hedging purpose 1 ￦ 20,627 ￦ — ￦ 20,627 ￦ (20,627 ) ￦ — ￦ — Trade payables 2 90,435 — 90,435 (86,184 ) — 4,251 Other payables 2 48 (4 ) 44 — — 44 ￦ 111,110 ￦ (4 ) ￦ 111,106 ￦ (106,811 ) ￦ — ￦ 4,295 (In millions of Korean won) 2017 Gross Gross offset Net amounts position Amounts not offset Net Financial Cash Derivative liabilities for hedging purpose 1 ￦ 26,135 ￦ — ￦ 26,135 ￦ (3,284 ) ￦ — ￦ 22,851 Trade payables 2 80,829 (5,217 ) 75,612 (73,109 ) — 2,503 Other financial liabilities 5,549 (229 ) 5,320 (5,307 ) — 13 ￦ 112,513 ￦ (5,446 ) ￦ 107,067 ￦ (81,700 ) ￦ — ￦ 25,367 1 The amount applied with master netting arrangements under the standard contract of International Swap and Derivatives Association (ISDA). 2 The amount applied with netting arrangements under the reference offer of the telecommunication facility interconnection and sharing data among telecommunications companies.
Currency risk [Member]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As of December 31, 2015, 2016 and 2017, if the foreign exchange rate had strengthened/weakened by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of Income before tax Shareholders’ equity 2015.12.31 10 % ￦ (52,157 ) ￦ (45,632 ) -10 % 52,157 45,632 2016.12.31 10 % (28,134 ) (23,817 ) -10 % 28,134 23,817 2017.12.31 10 % (10,132 ) (7,273 ) -10 % 10,132 7,273
Summary of Details of Financial Assets and Liabilities in Foreign Currencies	Details of financial assets and liabilities in foreign currencies as of December 31, 2015, 2016 and 2017, are as follows: 2015 2016 2017 (In thousands) Financial Financial liabilities Financial Financial Financial Financial USD 183,254 2,351,003 210,474 2,536,090 236,476 1,908,831 SDR 1 444 849 311 737 306 738 JPY 73,716 40,279,411 80,555 21,802,051 28,267 21,801,443 GBP 8 888 1 151 — 74 EUR 29 29 40 2,571 186 3,625 DZD 2 — — 471 — 47 — CNY 15,562 107 15,262 381 46,555 10 UZS 3 — — 39,531 — 136,787 — RWF 4 — — 1,203 — 3,346 — IDR 5 — — 15,646,011 53,142,167 14,886,393 710,162 MMK 6 — — 2,750 — 84 — TZS 7 — — 29,987 — 317,348 — BWP 8 — — 15 — 42 — HKD 9 — 254 — — — BDT 9 6 — 69,473 — 38,074 — PLN 10 207,273 — 106,025 — 338 — VND 11 270,000 — 515,412 — 311,649 — CHF 12 — — — — — 12 1 Special Drawing Rights. 2 Algeria Dinar. 3 Uzbekistan Sum. 4 Rwanda Franc. 5 Indonesia Rupiah. 6 Myanmar Kyat. 7 Tanzanian Shilling. 8 Botswana Pula. 9 Bangladesh Taka. 10 Polish Zloty. 11 Vietnam Dong. 12 Confoederatio Helvetia Franc.
Equity price risk [Member]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As of December 31, 2015, 2016 and 2017, the Group is exposed to equity securities price risk because the securities held by the Group are traded in active markets. If the market prices had increased/decreased by 10% with all other variables held constant, the effects on profit before income tax and shareholders’ equity would have been as follows: (In millions of Korean won) Fluctuation of price Income before tax Equity 2015.12.31 10% ￦ — ￦ 3,469 -10% — (3,469 ) 2016.12.31 10% ￦ — ￦ 539 -10% — (539 ) 2017.12.31 10% ￦ — ￦ 686 -10% — (686 )
Interest rate risk [Member]
Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity	As of December 31, 2015, 2016 and 2017, if the market interest rate had increased/decreased by 100bp with other variables held constant, the effects on profit before income tax and shareholders’ equity would be as follows: (In millions of Korean won) Fluctuation of interest rate Income before tax Shareholders’ 2015.12.31 + 100 bp ￦ (3,601 ) ￦ (245 ) - 100 bp 3,615 (5,764 ) 2016.12.31 + 100 bp ￦ (3,456 ) ￦ (1,673 ) - 100 bp 3,445 (5,025 ) 2017.12.31 + 100 bp ￦ 1,942 ￦ 4,868 - 100 bp (1,954 ) (5,198 )

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Carrying Amount and Fair Value of Financial Instruments by Category	Carrying amount and fair value of financial instruments by category as of December 31, 2016 and 2017, are as follows: 2016 2017 (In millions of Korean won) Carrying Fair value Carrying Fair value Financial assets Cash and cash equivalents 1 ￦ ￦ ￦ ￦ Trade and other receivables 1 6,036,363 — 6,643,115 — Other financial assets Financial instruments at fair value through profit or loss 6,277 6,277 5,813 5,813 Derivative financial instruments for hedging purpose 227,318 227,318 7,389 7,389 Time deposits and others 1 716,769 — 1,333,317 — Held-to-maturity 30,143 30,143 151 151 Available-for-sale 2 299,001 299,001 319,402 319,402 ￦ ￦ ￦ ￦ Financial liabilities Trade and other liabilities 1 ￦ ￦ ￦ ￦ Borrowings 8,120,791 8,184,195 6,683,662 6,738,326 Other financial liabilities Financial instruments at fair value through profit or loss 1,973 1,973 5,051 5,051 Derivative financial instruments for hedging purpose 14,928 14,928 93,770 93,770 Other 1 91,763 — 87,670 — ￦ ￦ ￦ ￦ 1 The Group did not conduct fair value estimation since the book amount is a reasonable approximation of the fair value. 2 Equity instruments that do not have a quoted price in an active market are measured at cost because their fair value cannot be measured reliably and excluded from the fair value disclosures.
Summary of Available-for-sale Financial Assets Measured at Cost	Available-for-sale (In millions of Korean won) 2016 2017 K-Bank ￦ 36,500 ￦ — IBK-AUCTUS Green Growth Private Equity Fund 9,506 8,518 WALDEN No.6 Fund 4,710 4,670 TRANSLINK No.2 Fund 9,395 9,395 Storm IV Fund 7,550 8,453 CBC II Fund 8,601 7,298 Others 29,511 23,217 ￦ 105,773 ￦ 61,551
Summary of Fair Value Hierarchy Classifications of Financial Assets and Financial Liabilities That are Measured at Fair Value	Fair value hierarchy classifications of the financial assets and financial liabilities that are measured at fair value or its fair value is disclosed as of December 31, 2016 and 2017, are as follows: 2016 (In millions of Korean won) Level 1 Level 2 Level 3 Total Recurring fair value measurements Other financial assets Financial assets at fair value through profit or loss ￦ — ￦ — ￦ 6,277 ￦ 6,277 Derivative financial assets for hedging purpose — 227,318 — 227,318 Available-for-sale 5,387 5,725 287,889 299,001 5,387 233,043 294,166 532,596 Disclosed fair value Associates and joint ventures 3,940 — — 3,940 Investment properties 1 — — 1,962,779 1,962,779 3,940 — 1,962,779 1,966,719 ￦ 9,327 ￦ 233,043 ￦ 2,256,945 ￦ 2,499,315 Recurring fair value measurements Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ — ￦ 1,973 ￦ 1,973 Derivative financial liabilities for hedging purpose — 14,928 — 14,928 — 14,928 1,973 16,901 Disclosed fair value Borrowings — — 8,184,195 8,184,195 — — 8,184,195 8,184,195 ￦ — ￦ 14,928 ￦ 8,186,168 ￦ 8,201,096 2017 (In millions of Korean won) Level 1 Level 2 Level 3 Total Recurring fair value measurements Other financial assets Financial assets at fair value through profit or loss ￦ — ￦ — ￦ 5,813 ￦ 5,813 Derivative financial assets for hedging purpose — 7,389 — 7,389 Available-for-sale 6,859 5,466 307,077 319,402 6,859 12,855 312,890 332,604 Disclosed fair value Investment properties 1 — — 1,755,600 1,755,600 — — 1,755,600 1,755,600 ￦ 6,859 ￦ 12,855 ￦ 2,068,490 ￦ 2,088,204 Recurring fair value measurements Other financial liabilities Financial liabilities at fair value through profit or loss ￦ — ￦ — ￦ 5,051 ￦ 5,051 Derivative financial liabilities for hedging purpose — 76,045 17,725 93,770 — 76,045 22,776 98,821 Disclosed fair value Borrowings — — 6,738,326 6,738,326 — — 6,738,326 6,738,326 ￦ — ￦ 76,045 ￦ 6,761,102 ￦ 6,837,147 1 The highest and best use of a non-financial
Summary of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements	(b) Details of changes in Level 3 of the fair value hierarchy for the recurring fair value measurements are as follows: 2016 (In millions of Korean won) Financial assets profit or loss Available-for-sale Other derivative financial Beginning balance ￦ 18 ￦ 267,337 ￦ 2,006 Reclassification — 5,723 — Amount recognized in other comprehensive income — 15,099 — Purchases 13,461 1,561 — Amount recognized in profit or loss (7,184 ) (426 ) (33 ) Sales (18 ) (1,405 ) — Ending balance ￦ 6,277 ￦ 287,889 ￦ 1,973 2017 (In millions of Korean won) Financial assets at Available-for-sale Other derivative Derivative financial Beginning balance ￦ 6,277 ￦ 287,889 ￦ 1,973 ￦ — Reclassification — (277 ) — — Amount recognized in other comprehensive income — 58,450 — (1,909 ) Purchases — 85,287 — — Amount recognized in profit or loss (464 ) (113 ) 3,078 19,634 Sales — (124,159 ) — — Ending balance ￦ 5,813 ￦ 307,077 ￦ 5,051 ￦ 17,725
Summary of Valuation Techniques and Inputs	Valuation techniques and inputs used in the recurring, non-recurring 2016 (In millions of Korean won) Fair value Level Valuation techniques Assets Recurring fair value measurements Other financial assets Derivative financial assets for hedging purpose ￦ 227,318 2 Discounted cash flow model Available-for-sale 293,614 2,3 Discounted cash flow model Others 6,277 3 Discounted cash flow model Disclosed fair value Investment properties 1,962,779 3 Discounted cash flow model Liabilities Recurring fair value measurements Other financial liabilities Derivative financial liabilities for hedging purpose 14,928 2 Discounted cash flow model Other derivative financial liabilities 1,973 3 Discounted cash flow model Comparable Company Disclosed fair value Borrowings 8,184,195 3 Discounted cash flow model 2017 (In millions of Korean won) Fair value Level Valuation techniques Assets Recurring fair value measurements Other financial assets Derivative financial assets for hedging purpose ￦ 7,389 2 Discounted cash flow model Available-for-sale 312,543 2,3 Discounted cash flow model Others 5,813 3 Discounted cash flow model Disclosed fair value Investment properties 1,755,600 3 Discounted cash flow model Liabilities Recurring fair value measurements Other financial liabilities Derivative financial liabilities for hedging purpose 93,770 2,3 Hull-White Model, Discounted cash flow model Other derivative financial liabilities 5,051 3 Discounted cash flow model Comparable Company Analysis Disclosed fair value Borrowings 6,738,326 3 Discounted cash flow model
Summary of Details and Changes of Total Deferred Difference	In relation to this, details and changes of the total deferred difference for the years ended December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 2017 Other derivative Other derivative Other derivative Other derivative Beginning balance ￦ 11,293 ￦ — ￦ 8,470 ￦ — New transactions — — — 7,126 Disposal (2,823 ) — (2,823 ) (594 ) Ending balance ￦ 8,470 ￦ — ￦ 5,647 ￦ 6,532

Interests in Unconsolidated S80

Interests in Unconsolidated Structured Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Unconsolidated Structured Entities and Nature of Risks	Details of scale of unconsolidated structured entities and nature of the risks associated with an entity’s interests in unconsolidated structured entities as of December 31, 2016 and 2017, are as follows: (In millions of Korean won) 2016 Real Estate Finance PEF &Investment Asset-backed Total Total assets of Unconsolidated Structured Entities ￦ 1,075,471 ￦ 3,759,246 ￦ 2,841,886 ￦ 7,676,603 Assets recognized in statement of financial position Other financial assets ￦ 21,932 ￦ 60,782 ￦ — ￦ 82,714 Joint ventures and Associates 10,086 165,638 — 175,724 Total ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 Maximum loss exposure1 Investment Assets ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 Total ￦ 32,018 ￦ 226,420 ￦ — ￦ 258,438 1 Maximum exposure to loss includes the investments recognized in the Group’s financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others. (In millions of Korean won) 2017 Real Estate Finance PEF &Investment Asset-backed Total Total assets of Unconsolidated Structured Entities ￦ 1,426,620 ￦ 3,779,377 ￦ 2,619,445 ￦ 7,825,442 Assets recognized in statement of financial position Other financial assets ￦ 21,800 ￦ 52,666 — ￦ 74,466 Joint ventures and Associates 10,168 164,030 — 174,198 Total ￦ 31,968 ￦ 216,696 ￦ — ￦ 248,664 Maximum loss exposure1 Investment Assets ￦ 31,968 ￦ 216,696 — ￦ 248,664 Total ￦ 31,968 ￦ 216,696 ￦ — ￦ 248,664 1 Maximum exposure to loss includes the investments recognized in the Group’s financial statements and the amounts which are probable to be determined when certain conditions are met by agreements including purchase agreements, credit granting and others.

Information About Non-control81

Information About Non-controlling Interests (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Changes in Accumulated Non-controlling Interests	Profit or loss allocated to non-controlling non-controlling (In millions of Korean won) 2015 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 297,300 ￦ 27,032 ￦ (8,325 ) ￦ 873 ￦ 316,880 BC Card Co., Ltd. 30.46 % 292,931 62,943 (22,650 ) (10,303 ) 322,921 KT Powertel Co., Ltd. 55.15 % 70,231 (17,880 ) (1,118 ) (307 ) 50,926 KT Hitel Co.,Ltd. 36.30 % 51,136 (608 ) — 161 50,689 KT Telecop Co., Ltd. 13.18 % 104,821 (1,000 ) — (393 ) 103,428 (In millions of Korean won) 2016 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 316,880 ￦ 22,445 ￦ (8,279 ) ￦ (1,370 ) ￦ 329,676 BC Card Co., Ltd. 30.46 % 322,921 47,068 (44,637 ) 3,986 329,338 KT Powertel Co., Ltd. 55.15 % 50,926 112 — 713 51,751 KT Hitel Co.,Ltd. 35.27 % 50,689 1,274 — (165 ) 51,798 KT Telecop Co., Ltd. 13.18 % 103,428 19 — 85 103,532 (In millions of Korean won) 2017 Non- controlling Accumulated non-controlling Profit or loss non-controlling Dividend paid to non- controlling Others Accumulated non-controlling KT Skylife Co., Ltd. 49.73 % ￦ 329,676 ￦ 9,395 ￦ (9,817 ) ￦ (952 ) ￦ 328,302 BC Card Co., Ltd. 30.46 % 329,338 43,961 (29,490 ) (4,742 ) 339,067 KT Powertel Co., Ltd. 55.15 % 51,751 1,165 — 137 53,053 KT Hitel Co.,Ltd. 32.87 % 51,798 870 — 478 53,146 KT Telecop Co., Ltd. 13.18 % 103,532 381 — (445 ) 103,468
Summary of Financial Information on Subsidiaries	Summarized consolidated statements of financial position as of December 31, 2015, 2016 and 2017, are as follows: 2015 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel KT Hitel KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 36.30 % 13.18 % Current assets ￦ 279,480 ￦ 2,291,047 ￦ 65,739 ￦ 157,355 ￦ 58,457 Non-current 431,814 672,905 47,776 78,402 210,734 Current liabilities 143,511 1,882,363 16,016 33,656 82,353 Non-current 74,339 63,271 5,166 282 52,613 Equity 493,444 1,018,318 92,333 201,819 134,225 Accumulated non-controlling 316,880 322,921 50,926 50,689 103,428 Operating revenue 668,521 3,504,946 104,527 162,155 302,844 Profit or loss for the year 72,987 218,969 (32,417 ) 7,258 (7,593 ) Total comprehensive income 73,147 188,360 (32,417 ) 6,769 (7,593 ) The profit or loss allocated to non-controlling 27,032 62,943 (17,880 ) (608 ) (1,000 ) Cash flows from operating activities 157,762 128,927 (12,016 ) 22,556 36,216 Cash flows from investing activities (92,350 ) 73,118 10,691 (19,949 ) (91,846 ) Cash flows from financing activities before dividend paid to non-controlling (35,984 ) (75,121 ) (2,015 ) — (32,491 ) Dividend paid to non-controlling (8,325 ) (22,650 ) (1,118 ) — — Net (decrease)/increase in cash and cash equivalents 29,428 126,924 (3,340 ) 2,607 (88,121 ) 2016 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel Co., Ltd. KT Hitel Co., Ltd. KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 35.27 % 13.18 % Current assets ￦ 352,980 ￦ 2,945,584 ￦ 69,046 ￦ 158,210 ￦ 63,802 Non-current 424,968 705,480 44,679 90,992 201,751 Current liabilities 151,329 2,530,832 17,910 45,277 53,903 Non-current 80,123 71,571 1,989 1,664 78,441 Equity 546,496 1,048,661 93,826 202,261 133,209 Accumulated non-controlling 329,676 329,338 51,751 51,798 103,532 Operating revenue 668,945 3,567,512 81,390 198,994 315,948 Profit or loss for the year 68,863 163,131 202 4,298 143 Total comprehensive income 68,785 178,744 202 1,399 143 The profit or loss allocated to non-controlling 22,445 47,068 112 1,274 19 Cash flows from operating activities 155,399 92,818 7,271 28,987 60,461 Cash flows from investing activities (210,480 ) (37,313 ) (8,191 ) (33,238 ) (45,243 ) Cash flows from financing activities before dividend paid to non-controlling (16,647 ) (147,306 ) — — — Dividend paid to non-controlling (8,279 ) (44,637 ) — — — Gain or loss foreign currency translation — (178 ) — 3 — Net (decrease)/increase in cash and cash equivalents (71,728 ) (91,801 ) (920 ) (4,251 ) 15,218 2017 (In millions of Korean won) KT Skylife BC Card Co., Ltd. KT Powertel Co., Ltd. KT Hitel Co., Ltd. KT Telecop Co., Ltd. Non-controlling 49.73 % 30.46 % 55.15 % 32.87 % 13.18 % Current assets ￦ 324,632 ￦ 3,225,262 ￦ 73,527 ￦ 150,368 ￦ 73,023 Non-current 468,261 823,001 41,598 107,872 191,330 Current liabilities 185,995 2,868,669 18,450 49,922 90,569 Non-current 24,555 86,369 487 3,021 41,064 Equity 582,343 1,093,225 96,188 205,297 132,720 Accumulated non-controlling 328,302 339,067 53,053 53,146 103,468 Operating revenue 687,752 3,628,995 69,234 227,884 317,591 Profit or loss for the year 57,314 156,109 2,112 3,225 2,885 Total comprehensive income 55,586 141,719 2,362 3,036 (490 ) The profit or loss allocated to non-controlling 9,395 43,961 1,165 870 381 Cash flows from operating activities 99,269 108,203 13,895 28,320 57,262 Cash flows from investing activities (81,758 ) (568,518 ) (17,354 ) (36,086 ) (43,483 ) Cash flows from financing activities before dividend paid to non-controlling (19,739 ) (97,221 ) — — — Dividend paid to non-controlling (9,817 ) (29,490 ) — — — Gain or loss foreign currency translation — (184 ) — (47 ) — Net (decrease)/increase in cash and cash equivalents (2,228 ) (557,536 ) (3,459 ) (7,766 ) 13,779
Summary of Changes in Ownership Interest on the Equity Attributable to Owners	The effect of changes in the ownership interest on the equity attributable to owners of the Group during 2015, 2016 and 2017 is summarized as follows: (in millions of Korean won) 2015 2016 2017 Carrying amount of non-controlling ￦ — ￦ 4,022 ￦ (732 ) Consideration paid to non-controlling 2,699 7,347 6,173 Excess of consideration paid recognized in parent’s equity ￦ 2,699 ￦ 11,369 ￦ 5,441

Events after Reporting Period (

Events after Reporting Period (Tables)	12 Months Ended
	Dec. 31, 2017
Text block1 [abstract]
Summary of Public Bonds Issued After Reporting Period	Subsequent to the reporting period, public bonds issued are as follow: December 31, 2017 (in millions of Korean won) Issue date Carrying amount Interest rate Redemption date The 190-1st 2018.01.30 110,000 2.55 % 2021.01.29 The 190-2nd Public bond 2018.01.30 150,000 2.75 % 2023.01.30 The 190-3rd 2018.01.30 170,000 2.95 % 2028.01.30 The 190-4th 2018.01.30 70,000 2.93 % 2038.01.30

General Information - Additiona

General Information - Additional Information (Detail) - shares	Jul. 02, 2001	May 09, 1999
Disclosure of general information [line items]
Number of additional shares issued	55,502,161	24,282,195
Government Owned shares [member]
Disclosure of general information [line items]
Number of additional shares issued		20,813,311

General Information - Summary o

General Information - Summary of Consolidated Subsidiaries (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of subsidiaries [Line Items]
Total assets	₩ 29,745,439	₩ 30,664,298
Total liabilities	16,696,309	17,881,580
Operating revenues	23,546,929	23,120,878	₩ 22,699,856
Profit (loss) for the year	₩ 546,341	₩ 795,117	₩ 624,685
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	₩ 115,125	₩ 113,725	₩ 113,515
Type of Business	Trunk radio system business
Total liabilities	₩ 18,937	19,899	21,182
Location	Korea
Operating revenues	₩ 69,234	₩ 81,390	104,527
Controlling percentage ownership	44.80%	44.80%
Profit (loss) for the year	₩ 2,112	₩ 202	₩ (32,417)
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	₩ 59,344	₩ 64,318	₩ 77,141
Type of Business	Public telephone maintenance
Total liabilities	₩ 51,516	56,953	65,745
Location	Korea
Operating revenues	₩ 112,043	₩ 117,587	116,095
Controlling percentage ownership	91.40%	91.40%
Profit (loss) for the year	₩ 725	₩ (3,830)	₩ 3,449
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	₩ 142,797	₩ 156,993	₩ 160,314
Type of Business	Submarine cable construction and maintenance
Total liabilities	₩ 34,056	55,573	63,518
Location	Korea
Operating revenues	₩ 73,985	₩ 84,137	67,268
Controlling percentage ownership	39.30%	39.30%
Profit (loss) for the year	₩ 8,243	₩ 5,146	₩ 4,145
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	₩ 264,353	₩ 265,553	₩ 269,191
Type of Business	Security service
Total liabilities	₩ 131,633	132,344	134,966
Location	Korea
Operating revenues	₩ 317,591	₩ 315,948	302,844
Controlling percentage ownership	86.80%	86.80%
Profit (loss) for the year	₩ 2,885	₩ 143	₩ (7,593)
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	₩ 258,240	₩ 249,202	₩ 235,757
Type of Business	Data communication
Total liabilities	₩ 52,943	46,941	33,938
Location	Korea
Operating revenues	₩ 227,884	₩ 198,994	162,155
Controlling percentage ownership	67.10%	67.10%
Profit (loss) for the year	₩ 3,225	₩ 4,298	₩ 7,258
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., Ltd2
Total assets	₩ 29,281	₩ 32,863	₩ 31,879
Type of Business	Opening services of fixed line
Total liabilities	₩ 22,096	24,580	22,627
Location	Korea
Operating revenues	₩ 194,837	₩ 182,952	89,498
Controlling percentage ownership	67.30%	67.30%
Profit (loss) for the year	₩ 688	₩ 694	₩ (4,630)
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., Ltd2
Total assets	₩ 36,076	₩ 32,621	₩ 20,729
Type of Business	Opening services of fixed line
Total liabilities	₩ 26,412	24,282	10,567
Location	Korea
Operating revenues	₩ 232,996	₩ 218,602	110,129
Controlling percentage ownership	77.30%	77.30%
Profit (loss) for the year	₩ 875	₩ 772	₩ (5,055)
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 New Business Fund No.1 [Member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT New Business Fund No.
Type of Business	Investment fund
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%
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	₩ 4,048,263	₩ 3,651,065	₩ 2,963,952
Type of Business	Credit card business
Total liabilities	₩ 2,955,038	2,602,404	1,945,634
Location	Korea
Operating revenues	₩ 3,628,995	₩ 3,567,512	3,504,946
Controlling percentage ownership	69.50%	69.50%
Profit (loss) for the year	₩ 156,109	₩ 163,131	₩ 218,969
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 Network
Total assets	₩ 273,856	₩ 272,110	₩ 248,189
Type of Business	Call centre for financial sectors
Total liabilities	₩ 65,446	80,983	70,635
Location	Korea
Operating revenues	₩ 277,622	₩ 266,613	241,008
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 16,104	₩ 14,749	₩ 19,513
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.4
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.
Total assets	₩ 144,922	₩ 197,970	₩ 162,518
Type of Business	System integration and maintenance
Total liabilities	₩ 93,343	151,644	116,654
Location	Korea
Operating revenues	₩ 459,266	₩ 476,379	423,015
Controlling percentage ownership	95.50%	95.50%
Profit (loss) for the year	₩ 11,584	₩ 10,838	₩ 12,836
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	₩ 42,738	₩ 28,539	₩ 25,093
Type of Business	Mobile marketing
Total liabilities	₩ 28,489	18,466	17,980
Location	Korea
Operating revenues	₩ 24,610	₩ 19,922	19,352
Controlling percentage ownership	90.00%	90.00%
Profit (loss) for the year	₩ 4,097	₩ 2,865	₩ 1,728
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	₩ 242,388	₩ 247,854	₩ 256,246
Type of Business	PCS distribution
Total liabilities	₩ 231,151	227,507	217,892
Location	Korea
Operating revenues	₩ 734,420	₩ 724,144	853,011
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (9,707)	₩ (12,955)	₩ (18,776)
Closing month	December
G E N I E 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	42.50%	49.90%
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.
Total assets	₩ 792,893	₩ 777,948	₩ 711,294
Type of Business	Satellite broadcasting business
Total liabilities	₩ 210,550	231,452	217,850
Location	Korea
Operating revenues	₩ 687,752	₩ 668,945	668,521
Controlling percentage ownership	50.30%	50.30%
Profit (loss) for the year	₩ 57,314	₩ 68,863	₩ 72,987
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.
Total assets	₩ 1,869,194	₩ 1,734,729	₩ 1,603,438
Type of Business	Residential building development and supply
Total liabilities	₩ 502,915	375,341	260,292
Location	Korea
Operating revenues	₩ 428,446	₩ 405,417	254,776
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 52,416	₩ 46,815	₩ 27,487
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	₩ 18,306	₩ 20,075	₩ 23,063
Type of Business	Data centre development and related service
Total liabilities	₩ 605	759	1,730
Location	Korea
Operating revenues	₩ 4,950	₩ 5,136	4,390
Controlling percentage ownership	51.00%	51.00%
Profit (loss) for the year	₩ (1,651)	₩ (1,983)	₩ (2,444)
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	₩ 742,391	₩ 744,653	₩ 679,959
Type of Business	Satellite communication business
Total liabilities	₩ 220,804	253,041	210,110
Location	Korea
Operating revenues	₩ 147,649	₩ 144,594	133,326
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 29,601	₩ 36,266	₩ 27,174
Closing month	December
K T Innoedu Co [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT Innoedu Co		KT Innoedu Co., Ltd.
Total assets			₩ 5,858
Type of Business	E-learning business
Total liabilities			7,585
Location	Korea
Operating revenues			18,156
Controlling percentage ownership		96.80%
Profit (loss) for the year			₩ (4,288)
Closing month	December
Nasmedia, Inc. [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	Nasmedia, Inc.	Nasmedia, Inc.	Nasmedia, Inc.
Total assets	₩ 315,967	₩ 263,925	₩ 141,733
Type of Business	Online advertisement
Total liabilities	₩ 188,197	159,502	72,202
Location	Korea
Operating revenues	₩ 120,667	₩ 70,037	45,630
Controlling percentage ownership	42.80%	42.80%
Profit (loss) for the year	₩ 26,676	₩ 11,972	₩ 9,916
Closing month	December
KT sports [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT Sports	KT Sports	KT Sports
Total assets	₩ 11,131	₩ 16,925	₩ 15,341
Type of Business	Management of sports group
Total liabilities	₩ 7,805	13,573	11,643
Location	Korea
Operating revenues	₩ 53,357	₩ 48,476	51,801
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (199)	₩ (198)	₩ (3,836)
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	₩ 13,804	₩ 10,592	₩ 10,206
Type of Business	Music contents investment business
Total liabilities	₩ 1,041	331	47
Location	Korea
Operating revenues	₩ 370	₩ 349	468
Controlling percentage ownership	80.00%	80.00%
Profit (loss) for the year	₩ (499)	₩ 103	₩ (111)
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%
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	₩ 14,575	₩ 16,250	₩ 5,401
Type of Business	Content investment business
Total liabilities	₩ 147	163
Location	Korea
Operating revenues	₩ 159	₩ 133	861
Controlling percentage ownership	88.60%	88.60%
Profit (loss) for the year	₩ (426)	₩ (514)	₩ (209)
Closing month	December
Autopion Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	Autopion Co., Ltd.	Autopion Co., Ltd.	Autopion Co., Ltd.
Total assets	₩ 6,306	₩ 6,163	₩ 7,102
Type of Business	Service for information and communication
Total liabilities	₩ 3,530	2,794	3,317
Location	Korea
Operating revenues	₩ 6,679	₩ 7,772	10,585
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (618)	₩ (409)	₩ 1,123
Closing month	December
KTCS Corporation [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KTCS Corporation	KTCS Corporation	KTCS Corporation
Total assets	₩ 348,334	₩ 322,768	₩ 346,949
Type of Business	Database and online information provider
Total liabilities	₩ 188,764	166,642	194,367
Location	Korea
Operating revenues	₩ 968,186	₩ 955,050	1,066,556
Controlling percentage ownership	30.90%	30.90%
Profit (loss) for the year	₩ 7,385	₩ 7,892	₩ 13,685
Closing month	December
KTIS Corporation [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KTIS Corporation	KTIS Corporation	KTIS Corporation
Total assets	₩ 223,818	₩ 221,176	₩ 211,164
Type of Business	Database and online information provider
Total liabilities	₩ 62,569	63,871	55,370
Location	Korea
Operating revenues	₩ 438,597	₩ 436,914	473,892
Controlling percentage ownership	30.10%	30.10%
Profit (loss) for the year	₩ 8,337	₩ 9,991	₩ 15,041
Closing month	December
KT M mobile [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT M mobile	KT M mobile	KT M mobile
Total assets	₩ 93,601	₩ 131,446	₩ 64,756
Type of Business	Special category telecommunications operator and sales of communication device
Total liabilities	₩ 21,453	20,369	13,121
Location	Korea
Operating revenues	₩ 159,684	₩ 112,532	42,478
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (38,883)	₩ (40,041)	₩ (36,725)
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
Total assets	₩ 54,673	₩ 39,506	₩ 49,485
Type of Business	Technology business finance
Total liabilities	₩ 38,313	23,123	30,827
Location	Korea
Operating revenues	₩ 8,794	₩ 10,130	4,704
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (619)	₩ (1,832)	₩ (219)
Closing month	December
Ngen bio [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	NgenBio
Type of Business	Medicine and Pharmacy development business
Location	Belgium
Controlling percentage ownership		49.80%
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
KT Rwanda Networks Ltd. [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT Rwanda Networks Ltd.	KT Rwanda Networks Ltd.	Olleh Rwanda Networks Ltd.
Total assets	₩ 151,359	₩ 167,112	₩ 188,951
Type of Business	Network installation and management
Total liabilities	₩ 139,561	138,651	147,653
Location	Rwanda
Operating revenues	₩ 15,931	₩ 13,435	7,299
Controlling percentage ownership	51.00%	51.00%
Profit (loss) for the year	₩ (22,762)	₩ (31,455)	₩ (28,721)
Closing month	December
AOS Ltd. [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	AOS Ltd.	AOS Ltd.	Africa Olleh Services Ltd.
Total assets	₩ 9,437	₩ 10,025	₩ 11,928
Type of Business	System integration and maintenance
Total liabilities	₩ 4,519	3,179	12,187
Location	Rwanda
Operating revenues	₩ 8,952	₩ 14,481	8,712
Controlling percentage ownership	51.00%	51.00%
Profit (loss) for the year	₩ (682)	₩ (1,123)	₩ (923)
Closing month	December
KT Belgium [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT Belgium	KT Belguium	KT Belgium
Total assets	₩ 86,455	₩ 79,391	₩ 77,058
Type of Business	Foreign investment business
Total liabilities	₩ 8	₩ 7	4
Location	Belgium
Operating revenues	₩ 49
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (2)	₩ (67)	₩ (127)
Closing month	December
KT ORS Belgium [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT ORS Belgium	KT ORS Belgium	KT ORS Belgium
Total assets	₩ 1,769	₩ 2,013	₩ 1,996
Type of Business	Foreign investment business
Total liabilities	₩ 14	₩ 23	20
Location	Belgium
Operating revenues	₩ 10
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (10)	₩ (46)	₩ (75)
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	₩ 1,554	₩ 3,592	₩ 13,889
Type of Business	Foreign telecommunication business
Total liabilities	₩ 2,788	5,374	14,393
Location	Japan
Operating revenues	₩ 2,772	₩ 5,122	25,652
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 536	₩ (1,391)	₩ (248)
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	₩ 3,311	₩ 1,166	₩ 1,471
Type of Business	Electronic communication business
Total liabilities	₩ 2,268	2,378	1,817
Location	Poland
Operating revenues	₩ 67	₩ 21
Controlling percentage ownership	94.00%	75.00%
Profit (loss) for the year	₩ (3,456)	₩ (2,587)	₩ (328)
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	₩ 665	₩ 532	₩ 909
Type of Business	Foreign telecommunication business
Total liabilities	₩ 32	188	198
Location	China
Operating revenues	₩ 1,030	₩ 930	1,748
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 348	₩ 60	₩ (95)
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	₩ 30,312	₩ 34,197	₩ 29,402
Type of Business	Super iMax and East Telecom management
Total liabilities	₩ 50	73	27
Location	Netherlands
Operating revenues	₩ 206	₩ 166	161
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 169	₩ 85	₩ 118
Closing month	December
Super iMax LLC [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	Super iMax LLC	Super iMax LLC	Super iMax LLC
Total assets	₩ 3,449	₩ 10,308	₩ 14,962
Type of Business	Wireless high speed internet business
Total liabilities	₩ 4,886	6,734	8,186
Location	Uzbekistan
Operating revenues	₩ 7,314	₩ 10,759	8,291
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ (4,584)	₩ (1,802)	₩ (2,220)
Closing month	December
East Telecom LLC [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	East Telecom LLC	East Telecom LLC	East Telecom LLC
Total assets	₩ 11,672	₩ 31,885	₩ 30,833
Type of Business	Fixed line telecommunication business
Total liabilities	₩ 11,748	16,554	17,066
Location	Uzbekistan
Operating revenues	₩ 19,663	₩ 27,492	24,066
Controlling percentage ownership	91.00%	91.00%
Profit (loss) for the year	₩ (9,118)	₩ 3,257	₩ 664
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	₩ 3,694	₩ 4,464	₩ 6,016
Type of Business	Foreign telecommunication business
Total liabilities	₩ 791	1,306	1,378
Location	USA
Operating revenues	₩ 6,783	₩ 7,113	6,391
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 109	₩ 181	₩ 156
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	₩ 16	₩ 22
Type of Business	Foreign telecommunication business
Location	Indonesia
Controlling percentage ownership	99.00%	99.00%
Profit (loss) for the year	₩ (6)	₩ (7)	₩ (9)
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.
Total assets	₩ 2,578	₩ 1,571
Type of Business	Fixed line communication business
Total liabilities	₩ 1,497	956
Location	Hong Kong
Operating revenues	₩ 7,304	₩ 1,568
Controlling percentage ownership	100.00%	100.00%
Profit (loss) for the year	₩ 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
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	₩ 139,686	₩ 110,080	₩ 90,518
Total liabilities	48,512	41,953	30,704
Operating revenues	156,163	111,450	90,005
Profit (loss) for the year	₩ (3,401)	₩ 8,235	₩ 3,446
NgeneBio [Member]
Disclosure of subsidiaries [Line Items]
Subsidiary		NgeneBio	NgeneBio
Total assets		₩ 6,361	₩ 7,894
Total liabilities		4,733	4,683
Operating revenues		244
Profit (loss) for the year		₩ (1,833)	₩ (434)
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
KT music contents fund number two [member]
Disclosure of subsidiaries [Line Items]
Subsidiary	KT Music Contents Fund No.2
Total assets	₩ 7,500
Total liabilities	11
Profit (loss) for the year	₩ (11)

Significant Accounting Polici85

Significant Accounting Policies - Additional Information (Detail) - KRW (₩) ₩ in Millions	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of significant accounting policies [line items]
Short-term lease description		A lease term of 12 months or less at the commencement date
Low value assets description		Underlying assets below $ 5,000
Loans and receivables		₩ 9,653,443
Financial assets available-for-sales		380,953	₩ 404,774	₩ 360,037
Debt instruments held with entity		9,653,594
Loss allowance recognized for credit losses of financial assets		523,799
Hedging instrument, assets		7,389
Hedging instrument, liabilities		₩ 93,770
Useful lives of investment property, excluding land depreciated cost model		10 to 40 Years
Minimum [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of significant accounting policies [line items]
Cumulative effect of change in operating income and expenses under modified retrospective method	₩ 900,000
Maximum [member] | Increase (decrease) due to changes in accounting policy required by IFRSs [member]
Disclosure of significant accounting policies [line items]
Cumulative effect of change in operating income and expenses under modified retrospective method	₩ 1,100,000
Available-for-sale [member]
Disclosure of significant accounting policies [line items]
Equity instruments held with entity		₩ 371,054
Loans and receivables [member]
Disclosure of significant accounting policies [line items]
Debt instruments held with entity		9,653,443
Held-to-maturity financial assets [member]
Disclosure of significant accounting policies [line items]
Debt instruments held with entity		₩ 151

Significant Accounting Polici86

Significant Accounting Policies - Summary of Estimated Useful Lives of Property, Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Buildings [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	5 - 40 years
Structures [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	5 - 40 years
Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	2 - 40 years
Vehicles [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	4 - 6 years
Tools [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	4 - 6 years
Office equipment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Estimated Useful Life	2 - 6 years

Significant Accounting Polici87

Significant Accounting Policies - Summary of Amortization of Intangible Assets With Limited Useful Life (Detail)	12 Months Ended
	Dec. 31, 2017
Development costs [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	5 - 6 years
Software [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	6 years
Frequency usage rights [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	5 - 10 years
Others [member]
Disclosure of detailed information about intangible assets [line items]
Estimated Useful Life	2 - 50 years

Financial Instruments by Cate88

Financial Instruments by Category - Summary of Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of detailed information about financial instruments [Line Items]
Trade and other payables	₩ 8,425,503	₩ 8,328,082
Borrowings	6,683,662	8,120,791
Other financial liabilities	186,490	108,664
Cash and cash equivalents	1,928,182	2,900,311	₩ 2,559,464	₩ 1,888,663
Trade and other receivables	6,643,115	6,036,363
Other financial assets	1,727,623	1,385,281
Loans and receivables [member]
Disclosure of detailed information about financial instruments [Line Items]
Cash and cash equivalents	1,928,182	2,900,311
Trade and other receivables	6,643,115	6,036,363
Other financial assets	1,333,317	716,769
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial assets	5,813	6,277
Derivatives contracts [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial liabilities	93,770	14,928
Other financial assets	7,389	227,318
Available-for-sale [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial assets	380,953	404,774
Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial assets	151	30,143
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial liabilities	5,051	1,973
Financial liabilities at amortized cost [member]
Disclosure of detailed information about financial instruments [Line Items]
Trade and other payables	8,425,503	8,328,082
Borrowings	6,683,662	8,120,791
Other financial liabilities	₩ 87,669	₩ 91,763

Financial Instruments by Cate89

Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Interest income	₩ 93,078	₩ 115,686	₩ 70,035
Interest expense	(302,464)	(337,219)	(385,925)
Dividend income	6,212	7,554
Total	(150,420)	(308,677)	(385,127)
Other comprehensive income for the year	(68,288)	(5,670)	(68,835)
Reclassified to profit or loss from other comprehensive income for the year	86,479	(79,384)
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Gain (loss) on disposal		(632)	(850)
Gain (loss) on valuation	(3,078)	33	(2,006)
Derivatives used for hedging [Member]
Disclosure of detailed information about financial instruments [Line Items]
Gain (loss) on transactions		8,329	(273)
Gain (loss) on valuation	(145,885)	(138)	(1,733)
Other comprehensive income for the year	(66,624)	4,295	11,513
Reclassified to profit or loss from other comprehensive income for the year	91,698	(3,956)	(9,959)
Financial liabilities at amortized cost [member]
Disclosure of detailed information about financial instruments [Line Items]
Interest expense	(302,464)	(337,219)	(385,925)
Gain (loss) foreign currency transaction	62,347	(7,518)	(23,416)
Gain(loss) foreign currency translation	225,695	(112,864)	(166,254)
Loans and receivables [member]
Disclosure of detailed information about financial instruments [Line Items]
Interest income	108,608	129,813	85,603
Gain (loss) foreign currency transaction	(11,949)	(7,493)	(365)
Gain(loss) on foreign currency translation	(12,354)	3,083	1,921
Gain (loss) on disposal	(20,351)	(15,838)	(2,539)
Gain (loss) on valuation	(44,219)	(92,589)	(141,555)
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Dividend income	1
Gain (loss) on disposal	153	186	368
Gain (loss) on valuation	(464)	(7,184)
Derivative liabilities for hedging purpose [Member]
Disclosure of detailed information about financial instruments [Line Items]
Gain (loss) on transactions	(58,569)		(5,157)
Gain (loss) on valuation	(63,640)	109,436	141,512
Other comprehensive income for the year	(44,429)	60,501	100,401
Reclassified to profit or loss from other comprehensive income for the year	50,231	(71,915)	(88,003)
Available-for-sale [member]
Disclosure of detailed information about financial instruments [Line Items]
Interest income	453	40	73
Dividend income	5,174	3,926	7,733
Gain (loss) on disposal	89,598	22,695	131,045
Impairment loss	(6,137)	(966)	(1,471)
Other comprehensive income for the year	51,235	10,925	47,381
Reclassified to profit or loss from other comprehensive income for the year	₩ (55,450)	(3,840)	(83,397)
Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Interest income		₩ 213	₩ 226

Financial Instruments by Cate90

Financial Instruments by Category - Summary of Gains or Losses Arising From Financial Instruments by Category (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Interest income recognized as operating revenue	₩ 93,078	₩ 115,686	₩ 70,035
BC Card Co., Ltd. [member]
Disclosure of detailed information about financial instruments [Line Items]
Interest income recognized as operating revenue	15,561	15,867	₩ 14,380
Operating income (expense)	₩ 11,049	₩ (1,987)

Cash and Cash Equivalents to Re

Cash and Cash Equivalents to Restricted Cash - Summary of Restricted Cash and Cash Equivalents (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Miscellaneous assets [abstract]
Deposit restricted for governmental project and others	₩ 16,837	₩ 19,920

Trade and Other Receivables - S

Trade and Other Receivables - Summary of Trade and Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Trade receivables	₩ 2,839,844	₩ 2,685,652
Other receivables	2,974,439	2,641,700
Trade and other receivables, net	5,814,283	5,327,352
Trade receivables	352,694	249,900
Other receivables	476,138	459,111
Trade and other receivables, net	828,832	709,011
Gross carrying amount [member]
Disclosure of financial assets [line items]
Trade receivables	3,286,169	3,161,234
Other receivables	3,041,028	2,763,942
Trade and other receivables, net	6,327,197	5,925,176
Trade receivables	366,107	263,367
Other receivables	522,459	507,251
Trade and other receivables, net	888,566	770,618
Allowance for doubtful accounts [member]
Disclosure of financial assets [line items]
Trade receivables	(438,817)	(470,239)
Other receivables	(66,402)	(121,972)
Trade and other receivables, net	(505,219)	(592,211)
Trade receivables	(610)	(632)
Other receivables	(17,970)	(19,644)
Trade and other receivables, net	(18,580)	(20,276)
Present value discount [member]
Disclosure of financial assets [line items]
Trade receivables	(7,508)	(5,343)
Other receivables	(187)	(270)
Trade and other receivables, net	(7,695)	(5,613)
Trade receivables	(12,803)	(12,835)
Other receivables	(28,351)	(28,496)
Trade and other receivables, net	₩ (41,154)	₩ (41,331)

Trade and Other Receivables -93

Trade and Other Receivables - Summary of Changes in Allowance for Doubtful Accounts (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of financial assets [line items]
Provision	₩ 523,799
Trade receivables [member]
Disclosure of financial assets [line items]
Beginning balance	470,871	₩ 468,741	₩ 527,617
Provision	38,888	84,975	95,489
Reversal or written-off	(70,121)	(80,518)	(135,318)
Changes in the scope of consolidation	(107)	215	(16,752)
Others	(104)	(2,542)	2,232
Ending balance	439,427	470,871	468,741
Other receivables [member]
Disclosure of financial assets [line items]
Beginning balance	141,616	250,842	311,082
Provision	5,809	7,736	46,066
Reversal or written-off	(61,220)	(108,638)	(33,282)
Changes in the scope of consolidation	(35)	56	(69,732)
Others	(1,798)	(8,380)	(3,272)
Ending balance	₩ 84,372	₩ 141,616	₩ 250,842

Trade and Other Receivables -94

Trade and Other Receivables - Summary of Aging Analysis of Trade Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Trade receivables	₩ 3,192,538	₩ 2,935,552
Gross carrying amount [member] | Neither past due nor impaired [member]
Disclosure of financial assets [line items]
Trade receivables	2,661,406	2,377,637
Gross carrying amount [member] | Past due and impaired [member]
Disclosure of financial assets [line items]
Trade receivables	970,559	1,028,786
Gross carrying amount [member] | Past due and impaired [member] | Up to 6 months [member]
Disclosure of financial assets [line items]
Trade receivables	701,032	685,288
Gross carrying amount [member] | Past due and impaired [member] | 6 months to 12 months [member]
Disclosure of financial assets [line items]
Trade receivables	70,190	87,547
Gross carrying amount [member] | Past due and impaired [member] | Over 12 months [member]
Disclosure of financial assets [line items]
Trade receivables	199,337	255,951
Allowance for doubtful accounts [member]
Disclosure of financial assets [line items]
Trade receivables	₩ (439,427)	₩ (470,871)

Trade and Other Receivables -95

Trade and Other Receivables - Summary of Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Loans	₩ 9,653,443
Other receivables	3,450,577	₩ 3,100,811
Other assets [member]
Disclosure of financial assets [line items]
Less Allowance for doubtful accounts	(84,372)	(141,616)
Gross carrying amount [member]
Disclosure of financial assets [line items]
Loans	84,682	80,308
Receivables	2,970,346	2,709,177
Accrued income	12,186	9,903
Refundable deposits	391,458	390,035
Loans receivable	34,273	10,355
Finance lease receivables	20,526	16,280
Others	₩ 21,478	₩ 26,369

Trade and Other Receivables -96

Trade and Other Receivables - Summary of Other Receivables (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
BC Card Co., Ltd. [member]
Disclosure of financial assets [line items]
Settlement receivable included in other receivables	₩ 2,262,829	₩ 1,962,880

Trade and Other Receivables -97

Trade and Other Receivables - Summary of Aging Analysis of Other Receivables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of financial assets [line items]
Other receivables	₩ 3,450,577	₩ 3,100,811
Other assets [member]
Disclosure of financial assets [line items]
Less Allowance for doubtful accounts	(84,372)	(141,616)
Gross carrying amount [member] | Neither past due nor impaired [member]
Disclosure of financial assets [line items]
Other receivables	3,271,949	2,971,239
Gross carrying amount [member] | Past due and impaired [member]
Disclosure of financial assets [line items]
Other receivables	263,000	271,188
Gross carrying amount [member] | Past due and impaired [member] | Up to 6 months [member]
Disclosure of financial assets [line items]
Other receivables	169,894	134,231
Gross carrying amount [member] | Past due and impaired [member] | 6 months to 12 months [member]
Disclosure of financial assets [line items]
Other receivables	16,052	12,805
Gross carrying amount [member] | Past due and impaired [member] | Over 12 months [member]
Disclosure of financial assets [line items]
Other receivables	₩ 77,054	₩ 124,152

Other Financial Assets and Li98

Other Financial Assets and Liabilities - Summary of Other Financial Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other financial assets
Financial assets at fair value through profit or loss	₩ 5,813	₩ 6,277
Derivatives used for hedge	7,389	227,318
Financial instruments	1,333,317	716,769
Available-for-sale financial assets	380,953	404,774	₩ 360,037
Held-to-maturity investments	151	30,143
Less: Non-current	(754,992)	(664,726)
Current	972,631	720,555
Other financial liabilities
Financial liabilities at fair value through the profit or loss	5,051	1,973
Derivatives used for hedge	93,770	14,928
Other financial liabilities	87,669	91,763
Less: Non-current	(149,267)	(108,431)
Current	₩ 37,223	₩ 233

Other Financial Assets and Li99

Other Financial Assets and Liabilities - Summary of Other Financial Assets and Liabilities (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Other financial assets	₩ 754,992	₩ 664,726
Ustream Inc. [member]
Disclosure of detailed information about financial instruments [Line Items]
Proceeds from the disposal of Subsidiary	59,660	₩ 49,721
Money Market Wrap and Money Market Trust [member] | Ustream Inc. [member]
Disclosure of detailed information about financial instruments [Line Items]
Other financial assets	₩ 870,453

Other Financial Assets and L100

Other Financial Assets and Liabilities - Summary of Financial Instruments at Fair Value Through Profit or Loss (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Assets	₩ 5,813	₩ 6,277
Liabilities	5,051	1,973
Financial instruments at fair value through profit and loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets	5,813	6,277
Other derivatives liabilities [member]
Disclosure of detailed information about financial instruments [Line Items]
Liabilities	₩ 5,051	₩ 1,973

Other Financial Assets and L101

Other Financial Assets and Liabilities - Summary of Financial Assets and Liabilities at Fair Value Through Profit or Loss (Detail) - Financial assets at fair value through profit or loss [member] - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Valuation gains		₩ 470
Valuation losses	₩ 464	₩ 7,654

Other Financial Assets and L102

Other Financial Assets and Liabilities - Summary of Financial Assets Held for Trading (Detail) - Financial assets at fair value through profit or loss, classified as held for trading, category [member] - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Valuation gains		₩ 33
Valuation losses	₩ 3,078		₩ 2,006

Other Financial Assets and L103

Other Financial Assets and Liabilities - Summary of Derivative Financial Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Assets, Total	₩ 7,389	₩ 227,318
Less: Assets, non-current	(4,675)	(97,220)
Assets, Current	2,714	130,098
Liabilities, Total	93,770	14,928
Less: Liabilities, non-current	(56,547)	(14,695)
Liabilities, Current	37,223	233
Interest rate swap [member]
Disclosure of detailed information about financial instruments [Line Items]
Liabilities, Total	2,633	3,278
Currency swap [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets, Total	7,389	214,648
Liabilities, Total	81,300	11,650
Currency forwards [member]
Disclosure of detailed information about financial instruments [Line Items]
Assets, Total		₩ 12,670
Liabilities, Total	₩ 9,837

Other Financial Assets and L104

Other Financial Assets and Liabilities - Summary of Valuation Gains and Losses on Derivatives Contracts (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Valuation gain	₩ 57	₩ 109,436	₩ 141,512
Valuation loss	209,582	138	1,733
Other comprehensive income	(146,508)	85,483	147,644
Interest rate swap [member]
Disclosure of detailed information about financial instruments [Line Items]
Valuation gain	38
Valuation loss		148
Other comprehensive income	637	(142)	(2,858)
Currency swap [member]
Disclosure of detailed information about financial instruments [Line Items]
Valuation gain	19	97,158	141,512
Valuation loss	187,468	(10)	1,733
Other comprehensive income	(146,752)	85,479	150,255
Currency forwards [member]
Disclosure of detailed information about financial instruments [Line Items]
Valuation gain		12,278
Valuation loss	22,114
Other comprehensive income	₩ (393)	₩ 146	₩ 247

Other Financial Assets and L105

Other Financial Assets and Liabilities - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Ineffective portion recognized in profit or loss cash flow hedge valuation gain	₩ 1,961	₩ 1,637	₩ 2,663
Korea Software Financial Cooperative [Member]
Disclosure of detailed information about financial instruments [Line Items]
Available-for-sale financial assets investment amount	₩ 1,000

Other Financial Assets and L106

Other Financial Assets and Liabilities - Summary of Available-For-Sale Financial Assets (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Financial assets available-for-sale	₩ 380,953	₩ 404,774	₩ 360,037
Less: non-current	(379,488)	(384,798)
Current	1,465	19,976
Marketable equity securities [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets available-for-sale	6,859	5,387
Non-marketable equity securities [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets available-for-sale	364,195	372,703
Debt securities [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets available-for-sale	₩ 9,899	₩ 26,684

Other Financial Assets and L107

Other Financial Assets and Liabilities - Summary of Changes in Available-for-Sale Financial Assets (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [abstract]
Beginning	₩ 404,774	₩ 360,037
Acquisition	89,027	44,302	₩ 99,111
Disposal	(129,682)	(18,161)
Valuation	67,593	14,413
Impairment	(6,137)	(966)
Reclassification	(44,622)	5,149
Changes in scope of consolidation	0	0
Ending	₩ 380,953	₩ 404,774	₩ 360,037

Inventories - Summary of Invent

Inventories - Summary of Inventories Net (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of inventories [line items]
Inventories	₩ 642,027	₩ 454,588
Merchandise [member]
Disclosure of inventories [line items]
Inventories	446,028	357,304
Others [member]
Disclosure of inventories [line items]
Inventories	195,999	97,284
Gross carrying amount [member]
Disclosure of inventories [line items]
Inventories	700,320	501,716
Gross carrying amount [member] | Merchandise [member]
Disclosure of inventories [line items]
Inventories	504,321	403,938
Gross carrying amount [member] | Others [member]
Disclosure of inventories [line items]
Inventories	195,999	97,778
Valuation allowance [member]
Disclosure of inventories [line items]
Inventories	(58,293)	(47,128)
Valuation allowance [member] | Merchandise [member]
Disclosure of inventories [line items]
Inventories	₩ (58,293)	(46,634)
Valuation allowance [member] | Others [member]
Disclosure of inventories [line items]
Inventories		₩ (494)

Inventories - Additional Inform

Inventories - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Classes of current inventories [abstract]
Inventories recognised as expense	₩ 3,855,089	₩ 3,589,809	₩ 3,760,892
Valuation loss and reversal of valuation loss	₩ 11,165	₩ (20,223)	₩ 4,116

Other Assets and Liabilities -

Other Assets and Liabilities - Summary of Other Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other assets
Advance payments	₩ 164,950	₩ 148,299
Prepaid expenses	241,078	255,464
Others	5,998	13,471
Less: Non-current	(107,165)	(106,099)
Current	304,860	311,135
Other liabilities
Advances received	375,792	281,071
Withholdings	85,142	89,679
Unearned revenue	23,036	24,142
Others	11,629	6,160
Less: Non-current	(237,284)	(58,761)
Current	₩ 258,315	₩ 342,291

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Changes in Property, Plant and Equipment (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	₩ 14,312,111	₩ 14,478,914
Acquisition	2,631,431	2,695,147
Disposal, Abandonment and termination	(196,138)	(126,152)
Depreciation	(2,755,236)	(2,778,204)
Impairment	(9,285)	(46,725)
Transfer in (out)	(310,687)
Exclusion from scope of consolidation	(945)
Inclusion in scope of consolidation		832
Transfer from (to) investment properties	(61,472)
Others	(47,460)	88,299
Ending, net	13,562,319	14,312,111
Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	43,133,769	42,220,319
Ending, net	43,626,804	43,133,769
Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(28,821,658)	(27,741,405)
Ending, net	(30,064,485)	(28,821,658)
Land [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,308,952	1,287,617
Acquisition	1,948	291
Disposal, Abandonment and termination	(4,656)	(855)
Transfer in (out)	26,764	4,274
Transfer from (to) investment properties	(64,449)
Others	98	17,625
Ending, net	1,268,657	1,308,952
Land [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,309,084	1,287,749
Ending, net	1,268,789	1,309,084
Land [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(132)	(132)
Ending, net	(132)	(132)
Buildings [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	2,124,732	2,099,044
Acquisition	120	3,608
Disposal, Abandonment and termination	(4,022)	(1,650)
Depreciation	(135,242)	(135,389)
Transfer in (out)	25,305	136,041
Exclusion from scope of consolidation	(19)
Transfer from (to) investment properties	1,793
Others	(245)	23,078
Ending, net	2,012,422	2,124,732
Buildings [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	3,729,228	3,558,460
Ending, net	3,750,861	3,729,228
Buildings [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(1,604,496)	(1,459,416)
Ending, net	(1,738,439)	(1,604,496)
Machinery and equipment1 [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	9,260,185	9,508,793
Acquisition	237,218	247,431
Disposal, Abandonment and termination	(176,085)	(112,135)
Depreciation	(2,469,459)	(2,498,837)
Impairment	(9,256)	361
Transfer in (out)	2,227,808	2,060,936
Exclusion from scope of consolidation	(772)
Inclusion in scope of consolidation		68
Others	(8,830)	53,568
Ending, net	9,060,809	9,260,185
Machinery and equipment1 [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	35,106,184	34,388,584
Ending, net	35,971,877	35,106,184
Machinery and equipment1 [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(25,845,999)	(24,879,791)
Ending, net	(26,911,068)	(25,845,999)
Others [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	524,923	550,983
Acquisition	129,464	146,471
Disposal, Abandonment and termination	(8,242)	(8,155)
Depreciation	(150,535)	(143,978)
Impairment	(1)	(47,086)
Transfer in (out)	10,344	11,073
Exclusion from scope of consolidation	(120)
Inclusion in scope of consolidation		764
Transfer from (to) investment properties	1,184
Others	(179)	14,851
Ending, net	506,838	524,923
Others [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,895,332	1,951,749
Ending, net	1,920,571	1,895,332
Others [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(1,370,409)	(1,400,766)
Ending, net	(1,413,733)	(1,370,409)
Construction-in-progress [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,093,319	1,032,477
Acquisition	2,262,681	2,297,346
Disposal, Abandonment and termination	(3,133)	(3,357)
Impairment	(28)
Transfer in (out)	(2,600,908)	(2,212,324)
Exclusion from scope of consolidation	(34)
Transfer from (to) investment properties	1,184
Others	(38,304)	(20,823)
Ending, net	713,593	1,093,319
Construction-in-progress [member] | Gross carrying amount [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	1,093,941	1,033,777
Ending, net	714,706	1,093,941
Construction-in-progress [member] | Accumulated depreciation, amortisation and impairment [member]
Disclosure of detailed information about property, plant and equipment [line items]
Beginning, net	(622)	(1,300)
Ending, net	₩ (1,113)	₩ (622)

Property, Plant and Equipmen112

Property, Plant and Equipment - Summary of the Details of Property, Plant and Equipment Provided (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [line items]
Related amount	₩ 6,683,662	₩ 8,120,791
Land and buildings [member]
Disclosure of detailed information about property, plant and equipment [line items]
Carrying amount	13,115	13,337
Secured amount	₩ 15,995	₩ 16,009
Related line item	Borrowings	Borrowings
Related amount	₩ 2,730	₩ 11,540
Secured party	Standard Chartered Bank Korea Development Bank	Standard Chartered Bank Korea Development Bank
Others [member]
Disclosure of detailed information about property, plant and equipment [line items]
Carrying amount	₩ 53,757	₩ 55,951
Secured amount	38,570	43,506
Related amount	₩ 16,071	₩ 25,379
Secured party	Shinhan Bank	Shinhan Bank

Property, Plant and Equipmen113

Property, Plant and Equipment - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about property, plant and equipment [line items]
Borrowing cost capitalized	₩ 8,473	₩ 16,451
Bottom of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Interest rate of capitalized borrowing cost	3.37%	2.29%
Top of range [member]
Disclosure of detailed information about property, plant and equipment [line items]
Interest rate of capitalized borrowing cost	3.54%	3.50%

Investment Properties - Summary

Investment Properties - Summary of Investment Properties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about investment property [line items]
Beginning balance	₩ 1,148,044	₩ 1,102,070
Acquisition	48,850	160,606
Disposal/Abandonment	(9,927)	(7,639)
Depreciation	(47,295)	(43,575)
Transfer from (to) property, plant and equipment	(61,472)
Transfer		(63,418)
Transfer and others	(11,613)
Ending balance	1,189,531	1,148,044
Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,501,400	1,426,234
Ending balance	1,590,018	1,501,400
Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about investment property [line items]
Beginning balance	(353,356)	(324,164)
Ending balance	(400,487)	(353,356)
Land [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	302,750	340,790
Acquisition		51
Disposal/Abandonment	(3,493)	(5,837)
Transfer from (to) property, plant and equipment	(64,449)
Transfer		(32,254)
Transfer and others	(6,916)
Ending balance	356,790	302,750
Land [member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	302,750	340,790
Ending balance	358,358	302,750
Land [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about investment property [line items]
Ending balance	(1,568)
Buildings [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	766,529	687,072
Acquisition	775	417
Disposal/Abandonment	(6,434)	(1,802)
Depreciation	(47,295)	(43,575)
Transfer from (to) property, plant and equipment	1,793
Transfer		124,417
Transfer and others	80,986
Ending balance	792,768	766,529
Buildings [member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	1,119,885	1,011,236
Ending balance	1,191,687	1,119,885
Buildings [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about investment property [line items]
Beginning balance	(353,356)	(324,164)
Ending balance	(398,919)	(353,356)
Construction-in-progress [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	78,765	74,208
Acquisition	48,075	160,138
Transfer from (to) property, plant and equipment	1,184
Transfer		(155,581)
Transfer and others	(85,683)
Ending balance	39,973	78,765
Construction-in-progress [member] | Gross carrying amount [member]
Disclosure of detailed information about investment property [line items]
Beginning balance	78,765	74,208
Ending balance	₩ 39,973	₩ 78,765

Investment Properties - Additio

Investment Properties - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about investment property [abstract]
Fair value of investment properties	₩ 1,755,600	₩ 1,962,779
Rental income from investment properties	₩ 205,993	₩ 184,670

Investment Properties - Summ116

Investment Properties - Summary of Investment Properties Provided as Collateral (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deposits 1 [Member] | Buildings [member]
Disclosure of detailed information about investment property [line items]
Carrying amount	₩ 772,708	₩ 711,989
Secured amount	₩ 104,861	₩ 98,543
Related account	Deposits	Deposits
Related amount	₩ 90,150	₩ 84,334
Borrowings [Member] | Land and buildings [member]
Disclosure of detailed information about investment property [line items]
Carrying amount	7,897	8,035
Secured amount	₩ 7,905	₩ 7,891
Related account	Borrowings	Borrowings
Related amount	₩ 5,270	₩ 5,260

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about intangible assets [line items]
Beginning, net	₩ 3,022,803	₩ 2,599,751
Acquisition and capital expenditure	386,711	1,124,327
Disposal and termination	(27,213)	(26,925)
Amortization	(635,150)	(599,721)	₩ (609,185)
Impairment	(116,095)	(135,264)
Inclusion in scope of consolidation	(4,922)	61,222
Others	6,570	(587)
Ending, net	2,632,704	3,022,803	2,599,751
Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	6,500,489	6,442,500
Ending, net	6,714,014	6,500,489	6,442,500
Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(3,477,686)	(3,842,749)
Ending, net	(4,081,310)	(3,477,686)	(3,842,749)
Goodwill [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	253,486	342,341
Impairment	(84,606)	(131,600)
Inclusion in scope of consolidation		42,745
Ending, net	168,880	253,486	342,341
Goodwill [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	492,105	449,379
Ending, net	474,908	492,105	449,379
Goodwill [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(238,619)	(107,038)
Ending, net	(306,028)	(238,619)	(107,038)
Development costs [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	334,676	461,543
Acquisition and capital expenditure	247,863	36,075
Disposal and termination	(14,806)	(8,600)
Amortization	(151,718)	(162,682)
Inclusion in scope of consolidation	(332)
Others	2,876	8,340
Ending, net	418,559	334,676	461,543
Development costs [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,483,205	1,487,420
Ending, net	1,643,886	1,483,205	1,487,420
Development costs [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(1,148,529)	(1,025,877)
Ending, net	(1,225,327)	(1,148,529)	(1,025,877)
Software [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	197,138	231,384
Acquisition and capital expenditure	60,475	35,631
Disposal and termination	(548)	(1,928)
Amortization	(73,174)	(78,643)
Impairment	(3)	(46)
Inclusion in scope of consolidation	(3,216)	2,462
Others	9,569	8,278
Ending, net	190,241	197,138	231,384
Software [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	838,532	805,387
Ending, net	893,500	838,532	805,387
Software [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(641,394)	(574,003)
Ending, net	(703,259)	(641,394)	(574,003)
Frequency usage rights [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,677,289	972,770
Acquisition and capital expenditure		978,309
Amortization	(311,146)	(273,790)
Others	(1,201)
Ending, net	1,364,942	1,677,289	972,770
Frequency usage rights [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	2,531,654	2,591,229
Ending, net	2,530,341	2,531,654	2,591,229
Frequency usage rights [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(854,365)	(1,618,459)
Ending, net	(1,165,399)	(854,365)	(1,618,459)
Others [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	560,214	591,713
Acquisition and capital expenditure	78,373	74,312
Disposal and termination	(11,859)	(16,397)
Amortization	(99,112)	(84,606)
Impairment	(31,486)	(3,618)
Inclusion in scope of consolidation	(1,374)	16,015
Others	(4,674)	(17,205)
Ending, net	490,081	560,214	591,713
Others [member] | Gross carrying amount [member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	1,154,993	1,109,085
Ending, net	1,171,378	1,154,993	1,109,085
Others [member] | Accumulated Depreciation and Amortisation [Member]
Disclosure of detailed information about intangible assets [line items]
Beginning, net	(594,779)	(517,372)
Ending, net	₩ (681,297)	₩ (594,779)	₩ (517,372)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about intangible assets [line items]
Indefinite useful life	₩ 238,053	₩ 268,350
Impairment losses recognized on indefinite-lived intangible assets	116,095	₩ 135,264	₩ 292,345
Satellite TV [member]
Disclosure of detailed information about intangible assets [line items]
Impairment losses recognized on goodwill	78,200
Impairment losses recognized on indefinite-lived intangible assets	₩ 29,325
Expected growth rate	0.00%
Estimated revenue growth rate	(0.77%)
Discount rate	13.25%

Intangible Assets - Summary 119

Intangible Assets - Summary of Goodwill Allocated to Each Cash-Generation Unit (Detail) ₩ in Millions	Dec. 31, 2017KRW (₩)
Disclosure of detailed information about intangible assets [line items]
Goodwill	₩ 168,880
Telecom Wireless Business [member] | Marketing [Member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	65,057
BC Card Co., Ltd. [member] | Finance [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	41,234
PlayD Co., Ltd. (N Search Marketing Co., Ltd.) [Member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	42,745
Genie Music Corporation (KT Music Corporation) and others [Member] | Others [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill	₩ 19,844

Intangible Assets - Summary 120

Intangible Assets - Summary of Goodwill Allocated to Each Cash-Generation Unit (Parenthetical) (Detail) - KRW (₩)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Mobile [member]
Disclosure of detailed information about intangible assets [line items]
Expected growth rate	0.00%
Estimated revenue growth rate	2.46%
Discount rate	8.95%
Impairment losses recognized on goodwill	₩ 0	₩ 0
BC Card Co., Ltd. [member]
Disclosure of detailed information about intangible assets [line items]
Expected growth rate	0.00%
Estimated revenue growth rate	0.11%
Discount rate	14.62%
Impairment losses recognized on goodwill	₩ 0	0
PlayD Co., Ltd. (N Search Marketing Co., Ltd.) [Member]
Disclosure of detailed information about intangible assets [line items]
Expected growth rate	1.00%
Estimated revenue growth rate	4.27%
Discount rate	9.50%
Impairment losses recognized on goodwill	₩ 0	₩ 0

Investments in Associates an121

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

Investments in Associates an122

Investments in Associates and Joint Ventures - Summary of Details of Associates (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
K Bank Inc. [member]
Disclosure of associates [line items]
Percentage of non-voting convertible stock are excluded	8.00%

Investments in Associates an123

Investments in Associates and Joint Ventures - Summary of Changes in Investments in Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of associates and joint ventures [line items]
Beginning	₩ 284,075	₩ 270,029
Acquisition (Disposal)	(19,018)	29,052
Share of net profit from associates and joint ventures	(15,480)	2,547
Impairment	(3,662)	(17,128)
Others	33,516	(425)
Ending	279,431	284,075
Korea Information & Technology Fund [member]
Disclosure of associates and joint ventures [line items]
Beginning	134,969	127,583
Share of net profit from associates and joint ventures	4,275	7,446
Others	290	(60)
Ending	139,534	134,969
KT-SB Venture Investment [member]
Disclosure of associates and joint ventures [line items]
Beginning	4,736	4,861
Acquisition (Disposal)	(1,069)
Share of net profit from associates and joint ventures	(725)	(125)
Ending	2,942	4,736
Mongolian Telecommunications [Member]
Disclosure of associates and joint ventures [line items]
Beginning	6,244	7,483
Share of net profit from associates and joint ventures	(348)	32
Others	(5,896)	(1,271)
Ending		6,244
KT Wibro Infra Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Beginning	52,200	69,328
Acquisition (Disposal)	(52,200)
Impairment		(17,128)
Ending		52,200
KT-CKP New Media Investment Fund [member]
Disclosure of associates and joint ventures [line items]
Beginning	4,454	3,860
Acquisition (Disposal)	(2,970)
Share of net profit from associates and joint ventures	810	594
Ending	2,294	4,454
Others [Member]
Disclosure of associates and joint ventures [line items]
Beginning	81,472	56,914
Acquisition (Disposal)	3,178	29,052
Share of net profit from associates and joint ventures	(1,952)	(5,400)
Impairment	(3,662)
Others	6,313	906
Ending	81,728	81,472
KT-IBKC future investment fund [member]
Disclosure of associates and joint ventures [line items]
Beginning	3,621
Acquisition (Disposal)	7,500
Share of net profit from associates and joint ventures	(296)
Ending	10,825	₩ 3,621
K Bank Inc. [member]
Disclosure of associates and joint ventures [line items]
Acquisition (Disposal)	26,543
Share of net profit from associates and joint ventures	(17,244)
Others	32,809
Ending	₩ 42,108

Investments in Associates an124

Investments in Associates and Joint Ventures - Summary of Changes in Investments in Associates and Joint Ventures (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of associates and joint ventures [line items]
Share gain from associates and joint ventures	₩ (13,892)	₩ 2,599	₩ 6,144
KT Investment Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Share gain from associates and joint ventures	₩ 1,588	₩ 52

Investments in Associates an125

Investments in Associates and Joint Ventures - Summary of Financial Information of Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of associates and joint ventures [line items]
Current assets	₩ 9,678,243	₩ 9,716,020
Non-current assets	20,067,196	20,948,278
Current liabilities	9,458,104	9,523,137
Non-current liabilities	7,238,205	8,358,443
Operating revenue	23,546,929	23,120,878	₩ 22,699,856
Profit (loss) for the year	546,341	795,117	624,685
Other comprehensive income	(68,288)	(5,670)	(68,835)
Total comprehensive income	478,053	789,447	₩ 555,850
Korea Information & Technology Fund [member]
Disclosure of associates and joint ventures [line items]
Current assets	144,874	154,651
Non-current assets	273,727	250,257
Operating revenue	36,462	26,942
Profit (loss) for the year	12,825	22,338
Other comprehensive income	1,868	(9,425)
Total comprehensive income	14,693	12,913
Dividend received from associates	739	3,201
KT-SB Venture Investment [member]
Disclosure of associates and joint ventures [line items]
Current assets	120	1,009
Non-current assets	5,770	8,704
Current liabilities	6	242
Operating revenue	3	2
Profit (loss) for the year	(1,449)	(251)
Total comprehensive income	(1,449)	(251)
Mongolian Telecommunications [Member]
Disclosure of associates and joint ventures [line items]
Current assets		9,852
Non-current assets		9,055
Current liabilities		3,296
Operating revenue		10,336
Profit (loss) for the year		81
Other comprehensive income		3,178
Total comprehensive income		3,259
KT Wibro Infra Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Current assets		274,811
Non-current assets		6
Current liabilities		4,996
Non-current liabilities		52
Operating revenue		391
Profit (loss) for the year		5,025
Total comprehensive income		5,025
KT-CKP New Media Investment Fund [member]
Disclosure of associates and joint ventures [line items]
Current assets	287	1,801
Non-current assets	4,333	7,170
Current liabilities		4
Operating revenue	1,593	1,684
Profit (loss) for the year	1,632	1,195
Total comprehensive income	1,632	₩ 1,195
KT-IBKC future investment fund [member]
Disclosure of associates and joint ventures [line items]
Current assets	5,499
Non-current assets	16,302
Current liabilities	152
Operating revenue	15
Profit (loss) for the year	(593)
Total comprehensive income	(593)
K Bank Inc. [member]
Disclosure of associates and joint ventures [line items]
Current assets	1,258,969
Non-current assets	92,137
Current liabilities	1,116,154
Non-current liabilities	1,177
Operating revenue	20,926
Profit (loss) for the year	(83,787)
Other comprehensive income	(746)
Total comprehensive income	₩ (84,533)

Investments in Associates an126

Investments in Associates and Joint Ventures - Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of associates and joint ventures [line items]
Carrying amount	₩ 279,431	₩ 284,075
Korea Information & Technology Fund [member]
Disclosure of associates and joint ventures [line items]
Net assets	₩ 418,601	₩ 404,908
Percentage of ownership	33.30%	33.30%
Share in net assets	₩ 139,534	₩ 134,969
Carrying amount	139,534	134,969
KT-SB Venture Investment [member]
Disclosure of associates and joint ventures [line items]
Net assets	₩ 5,884	₩ 9,471
Percentage of ownership	50.00%	50.00%
Share in net assets	₩ 2,942	₩ 4,736
Carrying amount	2,942	4,736
Mongolian Telecommunications [Member]
Disclosure of associates and joint ventures [line items]
Net assets		₩ 15,610
Percentage of ownership		40.00%
Share in net assets		₩ 6,244
Carrying amount		6,244
KT Wibro Infra Co., Ltd. [member]
Disclosure of associates and joint ventures [line items]
Net assets		₩ 269,769
Percentage of ownership		26.20%
Share in net assets		₩ 70,679
Carrying amount		52,200
KT Wibro Infra Co., Ltd. [member] | Material reconciling items [member]
Disclosure of associates and joint ventures [line items]
Share in net assets		(18,479)
KT-CKP New Media Investment Fund [member]
Disclosure of associates and joint ventures [line items]
Net assets	₩ 4,620	₩ 8,967
Percentage of ownership	49.70%	49.70%
Share in net assets	₩ 2,294	₩ 4,454
Carrying amount	2,294	₩ 4,454
KT-IBKC future investment fund [member]
Disclosure of associates and joint ventures [line items]
Net assets	₩ 21,649
Percentage of ownership	50.00%	50.00%
Share in net assets	₩ 10,825
Carrying amount	10,825
K Bank Inc. [member]
Disclosure of associates and joint ventures [line items]
Net assets	₩ 233,775
Percentage of ownership	10.00%
Share in net assets	₩ 42,108
Carrying amount	₩ 42,108

Investments in Associates an127

Investments in Associates and Joint Ventures - Summary of Reconciliation of Carrying Amount of Interests in the Associates and Joint Ventures (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2017
K Bank Inc. [member]
Disclosure of associates and joint ventures [line items]
Percentage of non-voting convertible stock are excluded	8.00%

Investments in Associates an128

Investments in Associates and Joint Ventures - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of associates [abstract]
Loss from associates and joint ventures not recognized	₩ 4,391	₩ 1,354	₩ 601
Accumulated comprehensive loss of associates and joint ventures not recognized	₩ 17,045	₩ 18,096	₩ 51,597

Trade and Other Payables - Summ

Trade and Other Payables - Summary of Trade and Other Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current liabilities
Trade payables	₩ 1,399,287	₩ 1,235,955
Other payables	6,024,847	5,903,816
Total	7,424,134	7,139,771
Non-current liabilities
Trade payables	4,787	8,041
Other payables	996,582	1,180,270
Total	₩ 1,001,369	₩ 1,188,311

Trade and Other Payables - S130

Trade and Other Payables - Summary of Other Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Trade and other payables [abstract]
Non-trade payables	₩ 4,773,223	₩ 4,803,642
Accrued expenses	1,011,089	1,061,002
Operating deposits	850,999	861,739
Others	386,118	357,703
Less: non-current	(996,582)	(1,180,270)
Current	₩ 6,024,847	₩ 5,903,816

Trade and Other Payables - S131

Trade and Other Payables - Summary of Other Payables (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Trade and other payables [abstract]
Settlement payables related to credit card transaction	₩ 2,365,477	₩ 2,095,989

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings (Detail) ¥ in Thousands, $ in Thousands, ₩ in Millions	12 Months Ended
	Dec. 31, 2017KRW (₩)	Dec. 31, 2017USD ($)	Dec. 31, 2017JPY (¥)	Dec. 31, 2016KRW (₩)	Dec. 31, 2016USD ($)	Dec. 31, 2016JPY (¥)
Disclosure of detailed information about borrowings [Line Items]
Less: Current portion	₩ (1,573,474)			₩ (1,820,001)
Borrowings	6,683,662			8,120,791
Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	6,703,009
Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Less: Current portion	(1,357,776)			(1,607,570)
Discount on bonds	(19,347)			(20,852)
Borrowings	4,610,453			5,715,878
Debentures [member] | Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 5,987,576			7,344,300
Debentures [member] | Gross carrying amount [member] | Sept. 07, 2034 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 07, 2034
Annual interest rates	6.50%	6.50%	6.50%
Borrowings	₩ 107,140	$ 100,000		120,850	$ 100,000
Debentures [member] | Gross carrying amount [member] | Jan. 20, 2017 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 20, 2017
Borrowings				422,975	350,000
Debentures [member] | Gross carrying amount [member] | Aug. 28, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Aug. 28, 2018
Annual interest rates description	LIBOR(3M)+1.15%
Annual interest rates adjustment rate	1.15%	1.15%	1.15%
Borrowings	₩ 321,420	$ 300,000		362,550	300,000
Debentures [member] | Gross carrying amount [member] | Apr. 22, 2017 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 22, 2017
Borrowings				785,525	650,000
Debentures [member] | Gross carrying amount [member] | Apr. 22, 2019 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 22, 2019
Annual interest rates	2.63%	2.63%	2.63%
Borrowings	₩ 374,990	$ 350,000		422,975	350,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 29, 2018
Annual interest rates	0.86%	0.86%	0.86%
Borrowings	₩ 64,539		¥ 6,800,000	70,503		¥ 6,800,000
Debentures [member] | Gross carrying amount [member] | Feb. 23, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Feb. 23, 2018
Annual interest rates	0.48%	0.48%	0.48%
Borrowings	₩ 142,367		¥ 15,000,000	155,522		¥ 15,000,000
Debentures [member] | Gross carrying amount [member] | July 18, 2026 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	July 18, 2026
Annual interest rates	2.50%	2.50%	2.50%
Borrowings	₩ 428,560	$ 400,000		483,400	$ 400,000
Debentures [member] | Gross carrying amount [member] | MTNP Notes August Seven Twenty Twenty Two [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Aug 07, 2022
Annual interest rates	2.63%	2.63%	2.63%
Borrowings	₩ 428,560	$ 400,000
Debentures [member] | Gross carrying amount [member] | Aug. 06, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Aug. 06, 2018
Annual interest rates	6.62%	6.62%	6.62%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Feb. 09, 2017 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Feb. 09, 2017
Borrowings				170,000
Debentures [member] | Gross carrying amount [member] | Mar. 29, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Mar. 29, 2018
Annual interest rates	4.47%	4.47%	4.47%
Borrowings	₩ 260,000			260,000
Debentures [member] | Gross carrying amount [member] | Apr. 26, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 26, 2021
Annual interest rates	4.71%	4.71%	4.71%
Borrowings	₩ 380,000			380,000
Debentures [member] | Gross carrying amount [member] | Aug. 26, 2016 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Aug. 26, 2018
Annual interest rates	3.99%	3.99%	3.99%
Borrowings	₩ 90,000			90,000
Debentures [member] | Gross carrying amount [member] | Aug. 26, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Aug. 26, 2021
Annual interest rates	4.09%	4.09%	4.09%
Borrowings	₩ 250,000			250,000
Debentures [member] | Gross carrying amount [member] | Oct. 28, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Oct. 28, 2021
Annual interest rates	4.31%	4.31%	4.31%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Dec. 22, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Dec. 22, 2021
Annual interest rates	4.09%	4.09%	4.09%
Borrowings	₩ 90,000			90,000
Debentures [member] | Gross carrying amount [member] | Dec. 22, 2031 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Dec. 22, 2031
Annual interest rates	4.27%	4.27%	4.27%
Borrowings	₩ 160,000			160,000
Debentures [member] | Gross carrying amount [member] | Apr. 10, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 10, 2018
Annual interest rates	2.74%	2.74%	2.74%
Borrowings	₩ 120,000			120,000
Debentures [member] | Gross carrying amount [member] | Apr. 10, 2023 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 10, 2023
Annual interest rates	2.95%	2.95%	2.95%
Borrowings	₩ 190,000			190,000
Debentures [member] | Gross carrying amount [member] | Apr. 10, 2033 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 10, 2033
Annual interest rates	3.17%	3.17%	3.17%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Sept. 16, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 16, 2018
Annual interest rates	3.46%	3.46%	3.46%
Borrowings	₩ 200,000			200,000
Debentures [member] | Gross carrying amount [member] | Sept. 16, 2020 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 16, 2020
Annual interest rates	3.65%	3.65%	3.65%
Borrowings	₩ 300,000			300,000
Debentures [member] | Gross carrying amount [member] | June 26, 2017 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	June 26, 2017
Borrowings				120,000
Debentures [member] | Gross carrying amount [member] | June 26, 2019 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	June 26, 2019
Annual interest rates	3.08%	3.08%	3.08%
Borrowings	₩ 170,000			170,000
Debentures [member] | Gross carrying amount [member] | June 26, 2024 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	June 26, 2024
Annual interest rates	3.42%	3.42%	3.42%
Borrowings	₩ 110,000			110,000
Debentures [member] | Gross carrying amount [member] | June 26, 2034 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	June 26, 2034
Annual interest rates	3.70%	3.70%	3.70%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2017 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 02, 2017
Borrowings				110,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2019 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 02, 2019
Annual interest rates	2.97%	2.97%	2.97%
Borrowings	₩ 220,000			220,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2024 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 02, 2024
Annual interest rates	3.31%	3.31%	3.31%
Borrowings	₩ 170,000			170,000
Debentures [member] | Gross carrying amount [member] | Sept. 02, 2034 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Sept. 02, 2034
Annual interest rates	3.55%	3.55%	3.55%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2020 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 29, 2020
Annual interest rates	2.26%	2.26%	2.26%
Borrowings	₩ 160,000			160,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2025 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 29, 2025
Annual interest rates	2.45%	2.45%	2.45%
Borrowings	₩ 240,000			240,000
Debentures [member] | Gross carrying amount [member] | Jan. 29, 2035 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 29, 2035
Annual interest rates	2.71%	2.71%	2.71%
Borrowings	₩ 50,000			50,000
Debentures [member] | Gross carrying amount [member] | Jan. 27, 2019 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 27, 2019
Annual interest rates	1.76%	1.76%	1.76%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Jan. 27, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 27, 2021
Annual interest rates	1.95%	1.95%	1.95%
Borrowings	₩ 130,000			130,000
Debentures [member] | Gross carrying amount [member] | Jan. 27, 2026 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 27, 2026
Annual interest rates	2.20%	2.20%	2.20%
Borrowings	₩ 100,000			100,000
Debentures [member] | Gross carrying amount [member] | Jan. 27, 2036 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Jan. 27, 2036
Annual interest rates	2.35%	2.35%	2.35%
Borrowings	₩ 70,000			70,000
Debentures [member] | Gross carrying amount [member] | Apr. 22, 2018 [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr. 22, 2018
Annual interest rates	1.89%	1.89%	1.89%
Borrowings	₩ 60,000			₩ 60,000

Borrowings - Summary of Borr133

Borrowings - Summary of Borrowings (Parenthetical) (Detail) ₩ in Millions	Dec. 31, 2017KRW (₩)	Dec. 31, 2017USD ($)	Dec. 31, 2016KRW (₩)
Disclosure of detailed information about borrowings [Line Items]
Borrowings | ₩	₩ 6,683,662		₩ 8,120,791
Libor rate	1.695%	1.695%
Medium Term Note Programme [member] | Fixed interest rate [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings		$ 100,000,000
Medium Term Note Programme [member] | Top of range [member] | Fixed interest rate [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings		$ 2,000,000,000

Borrowings - Summary of Short-t

Borrowings - Summary of Short-term Borrowings (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings	₩ 128,300	₩ 153,100
Shinhan Bank [Member]
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings	113,300	120,300
Standard Charted Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings		8,000
Korea Development Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings	12,000	20,800
Indutrial Bank of Korea [member]
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings		1,000
SooHyup Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Short-term borrowings	₩ 3,000	₩ 3,000
Short-term borrowings [member] | Shinhan Bank [Member] | Bottom of range [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.99%
Short-term borrowings [member] | Shinhan Bank [Member] | Top of range [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	4.41%
Short-term borrowings [member] | Korea Development Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.97%
Short-term borrowings [member] | SooHyup Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	4.22%

Borrowings - Summary of Long-te

Borrowings - Summary of Long-term Borrowings (Detail) $ in Thousands, ₩ in Millions	12 Months Ended
	Dec. 31, 2017KRW (₩)	Dec. 31, 2017USD ($)	Dec. 31, 2016KRW (₩)	Dec. 31, 2016USD ($)
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 6,683,662		₩ 8,120,791
Total	₩ 5,110,188		6,300,790
Shinhan Bank [Member] | Vessel facility loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates adjustment rate	1.695%	1.695%
Kookmin Bank [member] | Vessel facility loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates adjustment rate	1.695%	1.695%
Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 587,133		644,243
Less: Current portion	(87,398)		(59,331)
Total	₩ 499,735		584,912
Long-term borrowings [member] | Export-Import Bank of Korea [Member] | Inter-Korean Cooperation Fund [Member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	1.50%	1.50%
Borrowings	₩ 4,688		5,181
Long-term borrowings [member] | Shinhan Bank [Member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.50%	2.50%
Borrowings	₩ 30,000		31,000
Long-term borrowings [member] | Shinhan Bank [Member] | Facility loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.56%	2.56%
Borrowings	₩ 6,000		6,493
Long-term borrowings [member] | Shinhan Bank [Member] | Vessel facility loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates description	LIBOR(3M)+0.706%
Annual interest rates adjustment rate	0.706%	0.706%
Borrowings	₩ 16,071	$ 15,000	25,379	$ 21,000
Long-term borrowings [member] | KEB Hana Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.95%	3.95%
Borrowings	₩ 3,000		3,000
Long-term borrowings [member] | Woori Bank [Member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings			13,000
Long-term borrowings [member] | NongHyup Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.86%	2.86%
Borrowings	₩ 8,000
Long-term borrowings [member] | NongHyup Bank [member] | Facility loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.00%	2.00%
Borrowings	₩ 123		123
Long-term borrowings [member] | Korea Development Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.27%	3.27%
Borrowings	₩ 30,000		30,000
Long-term borrowings [member] | Kookmin Bank [member] | Facility loans [Member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	2.59%	2.59%
Borrowings	₩ 2,333		7,000
Long-term borrowings [member] | NH Investment & Security Co., Ltd. [member] | Commercial papers [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.17%	3.17%
Borrowings	₩ 300,000		300,000
Long-term borrowings [member] | Other Financial Instruments [member] | Redeemable convertible preferred stock [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 950		950
Long-term borrowings [member] | Other Financial Instruments [member] | Kookmin Bank and other [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.15%	3.15%
Borrowings	₩ 177,968	$ 166,108	₩ 222,117	$ 183,796
Long-term borrowings [member] | Standard Charted Bank [member] | General loans [member]
Disclosure of detailed information about borrowings [Line Items]
Annual interest rates	3.16%	3.16%
Borrowings	₩ 8,000

Borrowings - Summary of Long136

Borrowings - Summary of Long-term Borrowings (Parenthetical) (Detail) - ₩ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2010
Inter-Korean Cooperation Fund [Member]
Disclosure of detailed information about borrowings [Line Items]
Long term debt repayment	The Inter-Korean Cooperation Fund is repayable in installments over 13 years after a seven-year grace period.
Vessel facility loans [member] | Shinhan Bank [Member]
Disclosure of detailed information about borrowings [Line Items]
LIBOR rate	1.695%
Vessel facility loans [member] | Kookmin Bank [member]
Disclosure of detailed information about borrowings [Line Items]
LIBOR rate	1.695%
Redeemable convertible preferred stock [member]
Disclosure of detailed information about borrowings [Line Items]
Shares issued		1,900,000
Par value per share		₩ 500

Borrowings - Summary of Repayme

Borrowings - Summary of Repayment of Borrowings Including the Current Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 6,683,662	₩ 8,120,791
Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	4,610,453	5,715,878
Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	587,133	644,243
Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	6,703,009
Gross carrying amount [member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	5,987,576	₩ 7,344,300
Gross carrying amount [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	4,120,000
Gross carrying amount [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,867,576
Gross carrying amount [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	715,433
Gross carrying amount [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	521,394
Gross carrying amount [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	194,039
Gross carrying amount [member] | Over 12 months [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,574,024
Gross carrying amount [member] | Over 12 months [member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,358,326
Gross carrying amount [member] | Over 12 months [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	830,000
Gross carrying amount [member] | Over 12 months [member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	528,326
Gross carrying amount [member] | Over 12 months [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	215,698
Gross carrying amount [member] | Over 12 months [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	167,395
Gross carrying amount [member] | Over 12 months [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	48,303
Gross carrying amount [member] | Between 1-2 years [Member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,256,758
Gross carrying amount [member] | Between 1-2 years [Member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	864,990
Gross carrying amount [member] | Between 1-2 years [Member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	490,000
Gross carrying amount [member] | Between 1-2 years [Member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	374,990
Gross carrying amount [member] | Between 1-2 years [Member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	391,768
Gross carrying amount [member] | Between 1-2 years [Member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	343,465
Gross carrying amount [member] | Between 1-2 years [Member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	48,303
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	506,607
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	460,000
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	460,000
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	46,607
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,518
Gross carrying amount [member] | Jan 1, 2020 ~ Dec 31, 2020 [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	45,089
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	993,393
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	950,000
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	950,000
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	43,393
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,518
Gross carrying amount [member] | Jan 1, 2021 ~ Dec 31, 2021 [member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	41,875
Gross carrying amount [member] | More than 5 years [Member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	2,372,227
Gross carrying amount [member] | More than 5 years [Member] | Debentures [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	2,354,260
Gross carrying amount [member] | More than 5 years [Member] | Debentures [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	1,390,000
Gross carrying amount [member] | More than 5 years [Member] | Debentures [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	964,260
Gross carrying amount [member] | More than 5 years [Member] | Long-term borrowings [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	17,967
Gross carrying amount [member] | More than 5 years [Member] | Long-term borrowings [member] | In local currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	7,498
Gross carrying amount [member] | More than 5 years [Member] | Long-term borrowings [member] | In foreign currency [member]
Disclosure of detailed information about borrowings [Line Items]
Borrowings	₩ 10,469

Borrowings - Summary of Carryin

Borrowings - Summary of Carrying Amount and Fair Value of Debentures and Borrowings (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [Line Items]
Long-term borrowings (Including current portion of long-term borrowings)	₩ 6,683,662	₩ 8,120,791
Short-term borrowings	128,300	153,100
Gross carrying amount [member]
Disclosure of detailed information about borrowings [Line Items]
Debentures	5,968,229	7,323,448
Long-term borrowings (Including current portion of long-term borrowings)	587,133	644,243
Short-term borrowings	128,300	153,100
Total	6,683,662	8,120,791
Fair Value [member]
Disclosure of detailed information about borrowings [Line Items]
Debentures	6,022,551	7,387,085
Long-term borrowings (Including current portion of long-term borrowings)	587,475	644,010
Short-term borrowings	128,300	153,100
Total	₩ 6,738,326	₩ 8,184,195

Borrowings - Additional Informa

Borrowings - Additional Information (Detail)	Dec. 31, 2017	Dec. 31, 2016
Weighted average [member]
Disclosure of detailed information about borrowings [Line Items]
Weighted average borrowing rate	3.37%	3.38%

Provisions - Summary of Changes

Provisions - Summary of Changes in Provisions (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of other provisions [line items]
Beginning balance	₩ 197,179	₩ 195,272
Increase (transfer)	48,219	57,338
Usage	(26,300)	(41,396)
Reversal	(16,024)	(14,035)
Change in scope of consolidation	(44)
Ending balance	203,030	197,179
Current	78,172	96,485
Non-current	124,858	100,694
Litigation [member]
Disclosure of other provisions [line items]
Beginning balance	19,038	17,524
Increase (transfer)	3,842	3,392
Usage	(1,740)	(640)
Reversal	(2,834)	(1,238)
Ending balance	18,306	19,038
Current	17,238	18,988
Non-current	1,068	50
Restoration cost [member]
Disclosure of other provisions [line items]
Beginning balance	101,312	91,827
Increase (transfer)	2,827	13,653
Usage	(2,178)	(3,378)
Reversal	(1,723)	(790)
Change in scope of consolidation	(22)
Ending balance	100,216	101,312
Current	1,766	2,334
Non-current	98,450	98,978
Others [member]
Disclosure of other provisions [line items]
Beginning balance	76,829	85,921
Increase (transfer)	41,550	40,293
Usage	(22,382)	(37,378)
Reversal	(11,467)	(12,007)
Change in scope of consolidation	(22)
Ending balance	84,508	76,829
Current	59,168	75,163
Non-current	₩ 25,340	₩ 1,666

Net Defined Benefit Liabilit141

Net Defined Benefit Liabilities - Summary of Amount Recognized in the Statements of Financial Position (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of net defined benefit liability (asset) [abstract]
Present value of defined benefit obligations	₩ 1,911,166	₩ 1,713,184
Fair value of plan assets	(1,519,779)	(1,334,780)
Liabilities	395,079	₩ 378,404
Assets in the statement of financial position	₩ 3,692

Net Defined Benefit Liabilit142

Net Defined Benefit Liabilities - Summary of Changes in the Defined Benefit Obligations (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [Line Items]
Current service cost	₩ (210,336)	₩ (205,114)	₩ (200,994)
Interest expense	(8,691)	(12,141)	(16,793)
Present value of defined benefit obligation [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning balance	1,713,184	1,601,974
Current service cost	210,336	205,114
Interest expense	38,994	37,378
Benefit paid	(154,600)	(127,581)
Changes due to settlements of plan	(61)	(424)
Remeasurements:
Actuarial gains and losses arising from changes in demographic assumptions	3,353	(53,407)
Actuarial gains and losses arising from changes in financial assumptions	36,946	26,717
Actuarial gains and losses arising from experience adjustments	63,583	18,809
Changes in scope of consolidation	(569)	4,604
Ending balance	₩ 1,911,166	₩ 1,713,184	₩ 1,601,974

Net Defined Benefit Liabilit143

Net Defined Benefit Liabilities - Summary of Changes in the Fair Value of Plan Assets (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [Line Items]
Interest income	₩ (8,691)	₩ (12,141)	₩ (16,793)
Plan assets [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Beginning	1,334,780	1,077,891
Interest income	30,303	25,237
Remeasurements:
Return on plan assets (excluding amounts included in interest income)	(5,557)	(2,323)
Benefits paid	(130,510)	(88,876)
Employer contributions	290,895	322,851
Changes in scope of consolidation	(132)
Ending	₩ 1,519,779	₩ 1,334,780	₩ 1,077,891

Net Defined Benefit Liabilit144

Net Defined Benefit Liabilities - Additional Information (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2018KRW (₩)	Dec. 31, 2017KRW (₩)yr
Disclosure of net defined benefit liability (asset) [Line Items]
Expected contributions to post-employment benefit plans		₩ 197,942
Weighted average duration of the defined benefit obligations | yr		7.6
Subsequent event [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Estimation for expected employer contributions	₩ 197,942

Net Defined Benefit Liabilit145

Net Defined Benefit Liabilities - Summary of Amounts Recognized in the Statement of Profit or Loss (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in net defined benefit liability (asset) [abstract]
Current service cost	₩ 210,336	₩ 205,114	₩ 200,994
Net Interest cost	8,691	12,141	16,793
Past service cost	(61)	424
Transfer out	(9,196)	(8,737)	(11,942)
Transfer to discontinued operation			(3,031)
Total expenses	₩ 209,770	₩ 208,942	₩ 202,814

Net Defined Benefit Liabilit146

Net Defined Benefit Liabilities - Summary of Principal Actuarial Assumptions (Detail)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of defined benefit plans [abstract]
Discount rate	2.76%	2.43%	2.43%
Future salary increase	4.51%	4.10%	4.06%

Net Defined Benefit Liabilit147

Net Defined Benefit Liabilities - Summary of Sensitivity of the Defined Benefit Obligations (Detail) ₩ in Millions	Dec. 31, 2017KRW (₩)
Discount rate [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line items]
Percentage changes in assumption	0.50%
Effect on defined benefit obligation, increase in assumption	₩ (62,000)
Effect on defined benefit obligation, decrease in assumption	₩ 76,560
Salary growth rate [Member]
Disclosure of sensitivity analysis for actuarial assumptions [Line items]
Percentage changes in assumption	0.50%
Effect on defined benefit obligation, increase in assumption	₩ 71,273
Effect on defined benefit obligation, decrease in assumption	₩ (57,848)

Net Defined Benefit Liabilit148

Net Defined Benefit Liabilities - Summary of Expected Maturity Analysis of Undiscounted Pension Benefits (Detail) ₩ in Millions	Dec. 31, 2017KRW (₩)
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	₩ 4,713,478
Less than 1 year [member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	142,963
Between 1-2 years [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	179,612
Between 2-5 years [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	627,302
More than 5 years [Member]
Disclosure of net defined benefit liability (asset) [Line Items]
Pension benefits	₩ 3,763,601

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Classes of employee benefits expense [abstract]
Defined Contribution plan recognized expenses	₩ 45,936	₩ 46,023	₩ 35,699

Commitments and Contingencies -

Commitments and Contingencies - Summary of Major Commitments with Local Financial Institutions (Detail) - Dec. 31, 2017 $ in Thousands, ₩ in Millions	KRW (₩)	USD ($)
Disclosure of detailed information about borrowings [Line Items]
Limit	₩ 2,881,232	$ 253,500
Used amount	563,022	181,108
Bank overdraft [Member] | Kookmin Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	1,730,000
Used amount	72
Commercial papers [member] | NH Investment & Security Co., Ltd. [member]
Disclosure of detailed information about borrowings [Line Items]
Limit	370,000
Used amount	300,000
Collateralized loan on accounts receivable-trade [Member] | NongHyup Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Limit	35,560
Collateralised loans on electronic receivable-trade [Member] | Shinhan Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	343,000
Used amount	42,350
Plus electronic notes payable [Member] | Industrial Bank of Korea [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	50,000
Used amount	140
Loans for working capital [Member] | Korea Development Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	306,500
Used amount	207,300
Green energy factoring [Member] | Shinhan Bank [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	16
Used amount	16
FX forward trading commitment [Member] | Shinhan Bank [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit | $		11,500
Used amount | $		0
Facility loans [Member] | Kookmin Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	8,456	212,000
Used amount	8,456	166,108
Facility loans on ships [Member] | Shinhan Bank [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit | $		30,000
Used amount | $		$ 15,000
Inter-Korean Cooperation Fund [Member] | Export-Import Bank of Korea [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	37,700
Used amount	₩ 4,688

Commitments and Contingencie151

Commitments and Contingencies - Summary of Guarantees Received from Financial Institutions (Detail) - Dec. 31, 2017 zł in Thousands, $ in Thousands, ₩ in Millions	KRW (₩)	USD ($)	PLN (zł)
Disclosure of detailed information about borrowings [Line Items]
Limit	₩ 681,280	$ 69,141	zł 23,000
Performance guarantee [Member] | Seoul Guarantee Insurance and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	116,787	1,275
Guarantee for import letters of credit [Member] | Industrial Bank of Korea and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit | $		5,980
Guarantee for payment in foreign currency [Member] | KEB Hana Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit		54,072	zł 23,000
Guarantee for advances received [Member] | Export-Import Bank of Korea [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit | $		7,414
Comprehensive credit line [Member] | KEB Hana Bank and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	55,000
Bid guarantee [Member] | KEB Hana Bank [member]
Disclosure of detailed information about borrowings [Line Items]
Limit | $		$ 400
Bid guarantee [Member] | Korea Software Financial Cooperative [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	96,911
Performance guarantee/Warrant guarantee [Member] | Korea Software Financial Cooperative [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	302,062
Guarantee for advances received/Others [Member] | Korea Software Financial Cooperative and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	99,228
Warrant guarantee [Member] | Seoul Guarantee Insurance [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	2,962
Guarantees for licensing [Member] | Seoul Guarantee Insurance [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	4,077
Guarantees for public sale [Member] | Seoul Guarantee Insurance [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	50
Guarantees for deposits [Member] | Seoul Guarantee Insurance and others [Member]
Disclosure of detailed information about borrowings [Line Items]
Limit	₩ 4,203

Commitments and Contingencie152

Commitments and Contingencies - Summary of Guarantees Provided by the Group for Third Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [Line Items]
Used amount	₩ 6,683,662	₩ 8,120,791
Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Subject to payment guarantees	Daegu Beomeo -Crossroads SeohanIDaum Buyers
Limit	₩ 81,722
Used amount	₩ 14,237
Cash Payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Subject to payment guarantees	KEB Hana Bank
Limit	₩ 384
KT Estate Inc. [member] | Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Subject to payment guarantees	Busan Gaya Centreville Buyers
Limit	₩ 48,536
Used amount	₩ 8,309
Bottom of range [member] | Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Oct 29, 2017
Bottom of range [member] | Cash Payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr 19, 2017
Bottom of range [member] | KT Estate Inc. [member] | Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Nov 10, 2017
Top of range [member] | Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Nov. 30, 2020
Top of range [member] | Cash Payers [member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Apr 19, 2018
Top of range [member] | KT Estate Inc. [member] | Shinhan Bank [Member] | Guarantees [member]
Disclosure of detailed information about borrowings [Line Items]
Maturity	Oct. 31, 2020

Commitments and Contingencie153

Commitments and Contingencies - Additional Information (Detail) ₩ in Thousands	12 Months Ended
	Mar. 09, 2018KRW (₩)	Dec. 31, 2017KRW (₩)Lawsuits	Dec. 31, 2016KRW (₩)
Commitments and contingencies [abstract]
Severally liable for reimbursement		₩ 4,328,000
Number of lawsuits | Lawsuits		187
Litigation settlement claim amount		₩ 112,639,000	₩ 77,461,000
Litigation provision		18,306,000
Compensatory damages awarded to plaintiff	₩ 748,564,000
Interest on compensatory damages awarded	₩ 287,673,150
Interest rate on compensatory damages awarded delay	9.00%
Period for which compensatory damage settlement agreed	December 1, 2013 to March 9, 2018
Collaterally guarantees the debt		₩ 9,000,000
New town development consortium percentage of ownership interest		2.50%
Contract amount not yet recognized as liabilities		₩ 622,059,000	₩ 489,753,000

Lease - Summary of Details of F

Lease - Summary of Details of Finance Lease Assets (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of recognised finance lease as assets by lessee [Line Items]
Finance lease assets	₩ 199,884	₩ 193,618
Gross carrying amount [member]
Disclosure of recognised finance lease as assets by lessee [Line Items]
Finance lease assets	325,975	298,631
Accumulated Depreciation and Amortisation [Member]
Disclosure of recognised finance lease as assets by lessee [Line Items]
Finance lease assets	₩ (126,091)	₩ (105,013)

Lease - Additional Information

Lease - Additional Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about arrangements involving legal form of lease [abstract]
Depreciation property plant and equipment	₩ 58,535	₩ 50,704
Operating lease expenses incurred	₩ 126,250	₩ 121,852	₩ 111,776

Lease - Summary of Details o156

Lease - Summary of Details of Future Minimum Lease Payments under Finance Lease Contracts (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of finance lease and operating lease by lessee [Line Items]
Total amount of minimum lease payments	₩ 220,635	₩ 211,457
Unrealized interest expense	43,758	30,743
Net amount of minimum lease payments	176,877	180,714
Less than 1 year [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Total amount of minimum lease payments	88,441	79,644
Net amount of minimum lease payments	68,651	64,008
1-5 years [Member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Total amount of minimum lease payments	132,113	131,813
Net amount of minimum lease payments	108,146	₩ 116,706
More than 5 years [Member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Total amount of minimum lease payments	81
Net amount of minimum lease payments	₩ 80

Lease - Summary of Details o157

Lease - Summary of Details of Future Minimum Lease Payments under Operating Lease Contracts (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of finance lease and operating lease by lessee [Line Items]
Net amount of minimum lease payments	₩ 377,327	₩ 389,026
Less than 1 year [member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Net amount of minimum lease payments	109,258	102,015
1-5 years [Member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Net amount of minimum lease payments	266,434	270,462
More than 5 years [Member]
Disclosure of finance lease and operating lease by lessee [Line Items]
Net amount of minimum lease payments	₩ 1,635	₩ 16,549

Share Capital - Additional Info

Share Capital - Additional Information (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016
Disclosure of classes of share capital [abstract]
Number of authorized shares	1,000,000,000	1,000,000,000

Share Capital - Summary of Shar

Share Capital - Summary of Share Capital (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of classes of share capital [Line Items]
Ordinary Shares	₩ 1,564,499	₩ 1,564,499
Ordinary shares [member]
Disclosure of classes of share capital [Line Items]
Number of outstanding shares	261,111,808	261,111,808
2016 Par value per share	₩ 5,000	₩ 5,000
Ordinary Shares	₩ 1,564,499	₩ 1,564,499

Share Capital - Summary of S160

Share Capital - Summary of Share Capital (Parenthetical) (Detail) - ₩ / shares	Dec. 31, 2017	Dec. 31, 2016
Disclosure of classes of share capital [Line Items]
Treasury shares	51,787,959	51,787,959
Ordinary shares [member]
Disclosure of classes of share capital [Line Items]
Par value of shares issued	₩ 5,000	₩ 5,000

Retained Earnings - Summary of

Retained Earnings - Summary of Retained Earnings (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Miscellaneous equity [abstract]
Legal reserve	₩ 782,249	₩ 782,249
Voluntary reserves	4,651,362	4,651,362
Unappropriated retained earnings	4,393,315	4,210,872
Total	₩ 9,826,926	₩ 9,644,483

Retained Earnings - Summary 162

Retained Earnings - Summary of Retained Earnings (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2016
Miscellaneous equity [abstract]
Minimum percentage of cash dividend declared appropriation to legal reserve	10.00%
Percentage of legal reserve equal to capital stock issued	50.00%

Accumulated Other Comprehens163

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Accumulated Other Comprehensive Income (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total accumulated other comprehensive income	₩ 30,985	₩ (1,432)	₩ 13,870
Changes in investments in associates and joint ventures [member]
Total accumulated other comprehensive income	(735)	(10,883)	(10,312)
Loss on derivatives valuation [member]
Total accumulated other comprehensive income	(3,463)	(34,309)	(23,234)
Gain of valuation on available for sale [member]
Total accumulated other comprehensive income	52,673	54,106	52,415
Foreign currency translation adjustment [Member]
Total accumulated other comprehensive income	₩ (17,490)	₩ (10,346)	₩ (4,999)

Accumulated Other Comprehens164

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Beginning	₩ (1,432)	₩ 13,870
Increase /decrease	(54,062)	64,082
Reclassified to gain or loss	86,479	(79,384)
Ending	30,985	(1,432)
Changes in investments in associates and joint ventures [member]
Beginning	(10,883)	(10,312)
Increase /decrease	10,148	(571)
Ending	(735)	(10,883)
Loss on derivatives valuation [member]
Beginning	(34,309)	(23,234)
Increase /decrease	(111,083)	64,796
Reclassified to gain or loss	141,929	(75,871)
Ending	(3,463)	(34,309)
Gain of valuation on available for sale [member]
Beginning	54,106	52,415
Increase /decrease	54,017	5,204
Reclassified to gain or loss	(55,450)	(3,513)
Ending	52,673	54,106
Foreign currency translation adjustment [Member]
Beginning	(10,346)	(4,999)
Increase /decrease	(7,144)	(5,347)
Ending	₩ (17,490)	₩ (10,346)

Accumulated Other Comprehens165

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Other Components of Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Miscellaneous equity [abstract]
Treasury stock	₩ (853,108)	₩ (859,789)
Loss on disposal of treasury stock	873	607
Share-based payments	6,483	5,762
Others	(359,550)	(364,514)
Total	₩ (1,205,302)	₩ (1,217,934)

Accumulated Other Comprehens166

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Other Components of Equity (Parenthetical) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Miscellaneous equity [abstract]
Number of treasury shares granted	125,412
Treasury shares, Amount directly reflected in equity	₩ 653	₩ 738

Accumulated Other Comprehens167

Accumulated Other Comprehensive Income and Other Components of Equity - Summary of Treasury Stock (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Treasury Shares [abstract]
Number of shares	16,014,753	16,140,165
Amounts (In millions of Korean won)	₩ 853,108	₩ 859,789

Share-based Payments - Summary

Share-based Payments - Summary of Details of Share-based Payments (Detail) - KRW (₩)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Grant date	July 27, 2017
Vesting conditions	Service condition: 1 year Non-marketperformance condition: achievement of performance
Fair value per option	₩ 34,400
Total compensation costs	₩ 6,483,000,000	₩ 5,762,000,000

Share-based Payments - Summa169

Share-based Payments - Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning	318,506	263,123
Granted	316,949	373,419
Expired	193,094	181,685
Forfeited	0	0
Exercised	125,412	136,351
Ending	316,949	318,506
Number of shares exercisable	0	0
9th Grant [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning		263,123
Granted		54,913
Expired		181,685
Forfeited		0
Exercised		136,351
Number of shares exercisable		0
10th Grant [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Beginning	318,506
Granted		318,506
Expired	193,094
Forfeited	0	0
Exercised	125,412
Ending		318,506
Number of shares exercisable	0	0
11th grant [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Granted	316,949
Forfeited	0
Ending	316,949
Number of shares exercisable	0

Share-based Payments - Summa170

Share-based Payments - Summary of Changes in the Number of Stock Options and the Weighted-Average Exercise Price (Parenthetical) (Detail) - KRW (₩)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Weighted average price of ordinary shares	₩ 31,797	₩ 31,750

Operating Revenues - Summary of

Operating Revenues - Summary of Operating Revenues (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit or loss [abstract]
Services provided	₩ 19,898,725	₩ 19,935,865	₩ 19,455,693
Sale of goods	3,360,816	2,819,141	2,755,980
Others	287,388	365,872	488,183
Operating revenue	₩ 23,546,929	₩ 23,120,878	₩ 22,699,856

Operating Expenses - Summary of

Operating Expenses - Summary of Operating Expenses (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit or loss [abstract]
Salaries and wages	₩ 3,568,456	₩ 3,477,596	₩ 3,303,484
Depreciation	2,745,969	2,762,773	2,756,131
Amortization of intangible assets	618,533	582,493	582,467
Commissions	1,085,865	1,099,429	1,036,852
Interconnection charges	640,612	690,285	689,293
International interconnection fee	214,058	216,633	231,060
Purchase of inventories	4,053,693	3,407,263	3,963,036
Changes of inventories	(187,439)	162,323	(198,028)
Sales commission	2,201,778	1,968,035	1,856,595
Service cost	1,428,405	1,322,337	1,163,887
Utilities	323,313	323,406	319,303
Taxes and dues	279,574	255,480	256,958
Rent	448,772	455,457	469,950
Insurance premium	69,384	178,231	211,104
Installation fee	146,783	156,669	249,413
Advertising expenses	197,114	185,560	177,348
Research and development expenses	168,635	167,881	183,821
Card service cost	3,094,894	3,049,559	2,959,765
Others	1,379,438	1,319,688	1,410,349
Total	₩ 22,477,837	₩ 21,781,098	₩ 21,622,788

Operating Expenses - Summary173

Operating Expenses - Summary of Details of Employee Benefits (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit or loss [abstract]
Short-term employee benefits	₩ 3,297,944	₩ 3,206,904	₩ 3,055,699
Post-employment benefits (Defined benefit plan)	209,770	208,942	202,814
Post-employment benefits (Defined contribution plan)	45,936	46,023	35,699
Post-employment benefits (Others)	6,949	8,017	5,535
Share-based payment	7,660	7,710	3,737
Total	₩ 3,568,259	₩ 3,477,596	₩ 3,303,484

Financial Income and Costs - Su

Financial Income and Costs - Summary of Details of Financial Income (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Profit or loss [abstract]
Interest income	₩ 93,078	₩ 115,686	₩ 70,035
Gain on foreign currency transactions	79,653	24,915	18,766
Gain on foreign currency translation	225,580	12,165	11,280
Gain on settlement of derivatives		8,515	368
Gain on valuation of derivatives	57	109,436	141,512
Others	7,960	25,422	30,899
Total	₩ 406,328	₩ 296,139	₩ 272,860

Financial Income and Costs -175

Financial Income and Costs - Summary of Details of Financial Expense (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Finance Income [line items]
Interest expenses	₩ 302,464	₩ 337,219	₩ 385,925
Loss on foreign currency transactions	40,303	37,936	42,831
Loss on foreign currency translation	12,239	121,949	175,613
Loss on settlement of derivatives	58,569	632	6,280
Loss on valuation of derivatives	209,582	138	1,733
Impairment loss on available-for-sale financial assets	6,137	966
Others	1,010	409	28,605
Total	644,531	515,087	645,331
Loans and receivables [member]
Disclosure Of Finance Income [line items]
Loss on disposal of trade receivables	20,351	15,838	2,539
Available-for-sale [member]
Disclosure Of Finance Income [line items]
Loss on disposal of trade receivables	(89,598)	(22,695)	(131,045)
Impairment loss on available-for-sale financial assets	₩ 9	₩ 966	₩ 1,805

Deferred Income Tax and Inco176

Deferred Income Tax and Income Tax Expense - Summary of Analysis of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	₩ 712,222	₩ 701,409
Deferred income tax liabilities	128,462	137,680
Gross carrying amount [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	1,458,591	1,390,417
Deferred income tax liabilities	(874,831)	(826,688)
Gross carrying amount [member] | Less than 1 year [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	318,339	265,997
Deferred income tax liabilities	(15,705)	(48,033)
Gross carrying amount [member] | Over 12 months [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred income tax assets	1,140,252	1,124,420
Deferred income tax liabilities	₩ (859,126)	₩ (778,655)

Deferred Income Tax and Inco177

Deferred Income Tax and Income Tax Expense - Summary of Gross Movements on the Deferred Income Tax Account (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets and liabilities [abstract]
Beginning	₩ 563,729	₩ 715,747
Charged(credited) to the statement of profit or loss	(1,771)	(152,102)	₩ (232,134)
Charged(credited) to other comprehensive income	21,802	84
Ending	₩ 583,760	₩ 563,729	₩ 715,747

Deferred Income Tax and Inco178

Deferred Income Tax and Income Tax Expense - Summary of Movement in Deferred Income Tax Assets and Liabilities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	₩ 563,729	₩ 715,747
Statement of operations	(1,771)	(152,102)	₩ (232,134)
Other comprehensive income	21,802	84
Ending	583,760	563,729	715,747
Deferred tax derivative liabilities [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(49,188)	(19,155)
Statement of operations	49,188	(33,569)
Other comprehensive income		3,536
Ending		(49,188)	(19,155)
Deferred tax liabilities available for sale financial assets [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(31,702)	(29,430)
Statement of operations	(164)	(10)
Other comprehensive income	1,346	(2,262)
Ending	(30,520)	(31,702)	(29,430)
Deferred tax liabilities investment in subsidiaries associates and joint ventures [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(50,746)	(50,235)
Statement of operations	(42,659)	(666)
Other comprehensive income	(3,245)	155
Ending	(96,650)	(50,746)	(50,235)
Deferred tax liabilities depreciation [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(39,498)	(53,872)
Statement of operations	39,498	14,374
Ending		(39,498)	(53,872)
Deferred tax liabilities advanced depreciation provision [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(225,687)	(231,692)
Statement of operations	(22,905)	6,005
Ending	(248,592)	(225,687)	(231,692)
Deferred tax liabilities deposits for severance benefits [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(307,730)	(251,924)
Statement of operations	(80,126)	(55,806)
Ending	(387,856)	(307,730)	(251,924)
Deferred tax liabilities accrued income [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(2,024)	(1,808)
Statement of operations	(126)	(216)
Ending	(2,150)	(2,024)	(1,808)
Deferred tax liabilities reserve for technology and human resource development [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(747)	(1,216)
Statement of operations	433	469
Ending	(314)	(747)	(1,216)
Other deferred tax liabilities [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(119,366)	(135,802)
Statement of operations	10,617	16,436
Ending	(108,749)	(119,366)	(135,802)
Deferred tax liabilities [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	(826,688)	(775,134)
Statement of operations	(46,244)	(52,983)
Other comprehensive income	(1,899)	1,429
Ending	(874,831)	(826,688)	(775,134)
Deferred tax derivative assets [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Statement of operations	34,572
Other comprehensive income	(9,848)
Ending	24,724
Deferred tax assets provision for impairment on trade receivables [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	110,276	136,743
Statement of operations	11,380	(26,467)
Ending	121,656	110,276	136,743
Deferred tax assets inventory valuation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	48	56
Statement of operations	(48)	(8)
Ending		48	56
Deferred tax assets contribution for construction [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	18,091	19,618
Statement of operations	180	(1,527)
Ending	18,271	18,091	19,618
Deferred tax assets accrued expenses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	80,356	64,117
Statement of operations	10,683	16,239
Ending	91,039	80,356	64,117
Deferred Tax Assets Provisions [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	20,221	20,353
Statement of operations	3,858	(132)
Ending	24,079	20,221	20,353
Deferred tax assets property, plant and equipment [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	232,915	239,791
Statement of operations	(841)	(6,876)
Ending	232,074	232,915	239,791
Deferred tax assets retirement benefit obligations [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	372,492	331,980
Statement of operations	67,751	41,857
Other comprehensive income	26,806	(1,345)
Ending	467,049	372,492	331,980
Deferred tax assets withholding of facilities expenses [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	6,910	7,360
Statement of operations	472	(450)
Ending	7,382	6,910	7,360
Deferred tax assets accrued payroll expenses [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	25,915	21,634
Statement of operations	(10,786)	4,281
Ending	15,129	25,915	21,634
Deferred tax assets deduction of installment receivables [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	13,887	10,513
Statement of operations	(13,887)	3,374
Ending		13,887	10,513
Deferred Tax assets assets retirement obligation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	18,086	16,974
Statement of operations	2,750	1,112
Ending	20,836	18,086	16,974
Deferred tax assets gain or loss foreign currency translation [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	67,701	43,283
Statement of operations	(67,558)	24,418
Ending	143	67,701	43,283
Deferred tax assets deferred revenue [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	26,113	43,792
Statement of operations	221	(17,679)
Ending	26,334	26,113	43,792
Deferred tax assets real-estate sales [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	3,851	2,980
Statement of operations	4,847	871
Ending	8,698	3,851	2,980
Deferred tax assets tax credit carry forwards [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	199,599	212,820
Statement of operations	(48,823)	(13,221)
Ending	150,776	199,599	212,820
Deferred tax assets accumulated deficit [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning		107,485
Statement of operations		(107,485)
Ending			107,485
Deferred tax assets deficit carried over [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Statement of operations	2,699
Ending	2,699
Other deferred tax assets [member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	193,956	211,382
Statement of operations	47,003	(17,426)
Other comprehensive income	6,743
Ending	247,702	193,956	211,382
Deferred tax assets [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Beginning	1,390,417	1,490,881
Statement of operations	44,473	(99,119)
Other comprehensive income	23,701	(1,345)
Ending	₩ 1,458,591	₩ 1,390,417	₩ 1,490,881

Deferred Income Tax and Inco179

Deferred Income Tax and Income Tax Expense - Summary of Tax Impacts Recognized Directly To Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets and liabilities [abstract]
Available-for-sale valuation gain(loss), Before recognition	₩ (5,561)	₩ 9,347	₩ (47,515)
Hedge instruments valuation gain(loss), Before recognition	40,694	(14,611)	18,406
Remeasurements from net defined benefit liabilities, Before recognition	(110,768)	5,558	(49,963)
Shares of gain(loss) of associates and joint ventures, Before recognition	13,410	(641)	(5,297)
Foreign currency translation adjustment	(27,865)	(7,133)	(6,443)
Total, Before recognition	(90,090)	(7,480)	(90,812)
Available-for-sale valuation gain(loss), Tax effect	1,346	(2,262)	11,499
Hedge instruments valuation gain(loss), Tax effect	(9,848)	3,536	(4,454)
Remeasurements from net defined benefit liabilities, Tax effect	26,806	(1,345)	12,091
Shares of gain(loss) of associates and joint ventures, Tax effect	(3,245)	155	1,282
Foreign currency translation adjustment	6,743	1,726	1,559
Total, Tax effect	21,802	1,810	21,977
Available-for-sale valuation gain(loss), After recognition	(4,215)	7,085	(36,016)
Hedge instruments valuation gain(loss), After recognition	30,846	(11,075)	13,952
Remeasurements from net defined benefit liabilities, After recognition	(83,962)	4,213	(37,872)
Shares of gain(loss) of associates and joint ventures, After recognition	10,165	(486)	(4,015)
Foreign currency translation adjustment	(21,122)	(5,407)	(4,884)
Total other comprehensive loss	₩ (68,288)	₩ (5,670)	₩ (68,835)

Deferred Income Tax and Inco180

Deferred Income Tax and Income Tax Expense - Summary of Details of Income Tax Expense (Benefit) (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets and liabilities [abstract]
Current income tax expense(benefit)	₩ 268,885	₩ 176,212	₩ (5,003)
Impact of change in deferred taxes	1,771	152,102	232,134
Income tax expense	₩ 270,656	₩ 328,314	₩ 227,131

Deferred Income Tax and Inco181

Deferred Income Tax and Income Tax Expense - Summary of Tax on the Group's Profit Before Tax (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets and liabilities [abstract]
Profit before income tax expense	₩ 816,997	₩ 1,123,431	₩ 710,741
Statutory income tax expense	197,251	271,870	171,999
Tax effect
Income not taxable for taxation purposes	(19,268)	(28,093)	(21,881)
Non-deductible expenses	39,746	21,947	28,849
Tax credit	(27,211)	(13,764)	(9,660)
Additional payment of income taxes	976	(4,780)	997
Tax effect and adjustment on consolidation
Goodwill impairment	20,475	31,847	23,185
Eliminated dividend income form subsidiaries	34,305	40,087	20,452
Changes of out-side tax effect	17,990	(567)	9,844
Others	6,392	9,767	3,346
Income tax expense	₩ 270,656	₩ 328,314	₩ 227,131

Earnings per Share - Summary of

Earnings per Share - Summary of Basic and Diluted Earnings per Share from Operations (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic earnings per share [abstract]
Profit (loss) attributable to ordinary shares	₩ 461,559	₩ 708,362	₩ 546,361
Profit from continuing operations attributable to ordinary shares	₩ 461,559	₩ 708,362	404,045
Profit from discontinued operations attributable to ordinary shares			₩ 142,316
Weighted average number of ordinary shares outstanding	245,017,175	244,892,313	244,854,364
Basic earnings per share (In Korean won)	₩ 1,884	₩ 2,893	₩ 2,231
Basic earnings per share from continuing operations	₩ 1,884	₩ 2,893	1,650
Basic earnings per share from discontinued operations			₩ 581
Profit attributable to ordinary shares (In millions of Korean won)	₩ 461,559	₩ 708,362	₩ 546,361
Adjusted net income attributable to ordinary shares		(67)	(75)
Diluted profit attributable to ordinary shares (In millions of Korean won)	461,559	708,295	546,286
Diluted profit (loss) attributable to ordinary shares	461,559	708,295	546,286
Diluted profit from continuing operations attributable to ordinary shares	₩ 461,559	₩ 708,295	403,970
Diluted income from discontinued operations attributable to ordinary shares			₩ 142,316
Number of dilutive potential ordinary shares outstanding	79,880	84,245	1,104
Weighted average number of ordinary shares outstanding	245,097,055	244,976,558	244,855,468
Diluted earnings per share (In Korean won)	₩ 1,883	₩ 2,891	₩ 2,231
Diluted earnings per share from continuing operations	₩ 1,883	₩ 2,891	1,650
Diluted earnings per share from discontinued operations			₩ 581

Dividend - Additional Informati

Dividend - Additional Information (Detail) - KRW (₩) ₩ / shares in Units, ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Dividends [abstract]
Dividends paid	₩ 195,977	₩ 122,425	₩ 0
Dividends paid per share	₩ 800	₩ 500
Dividends declared	₩ 245,097
Dividends declared per share	₩ 1,000

Cash Generated from Operatio184

Cash Generated from Operations - Summary of Cash Flows from Operating Activities (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from (used in) operating activities [abstract]
Profit for the year	₩ 546,341	₩ 795,117	₩ 624,685
Adjustments to reconcile net income
Income tax expense	270,656	328,314	346,146
Interest income	(108,639)	(130,066)	(161,123)
Interest expense	302,464	337,219	445,814
Dividends income	(4,785)	(3,926)	(11,371)
Depreciation	2,802,531	2,821,779	3,030,821
Amortization of intangible assets	635,150	599,721	609,185
Provision for severance benefits	218,966	217,255	217,787
Impairment losses on trade receivables	45,704	92,711	161,448
Share of net profit or loss of associates and joint ventures	15,480	(2,547)	(5,562)
Loss(gain) on disposal of associates and joint ventures	979	(1,450)	(4,848)
Impairment loss of associates and joint ventures	3,662	17,128
Gain on disposal of subsidiaries			(256,230)
Loss on disposal of property, plant and equipment and investment in properties	150,293	74,913	129,466
Loss on disposal of intangible assets	4,271	7,703	33,978
Loss on impairment of intangible assets	116,095	135,264	292,345
Loss on foreign currency translation	(213,341)	109,784	164,374
Loss(gain) on valuation of derivatives	268,094	(117,181)	(306,538)
Impairment losses on available-for-sale financial assets	9	966	1,805
Gain on disposal of available-for-sale financial assets	(89,598)	(22,695)	(131,041)
Others	(251,193)	64,863	24,140
Changes in operating assets and liabilities
Decrease(increase) in trade receivables	(303,340)	252,196	112,674
Increase in other receivables	(346,013)	(770,893)	(21,749)
Decrease(increase) in other current assets	11,792	48,549	(19,701)
Increase in other non-current assets	(43,790)	(51,765)	(137,532)
Decrease(increase) in inventories	(205,403)	167,873	(270,343)
Increase(decrease) in trade payables	162,110	(114,838)	81,295
Increase(decrease) in other payables	214,689	705,807	(48,680)
Increase(decrease) in other current liabilities	288,553	37,798	(9,452)
Increase in other non-current liabilities	174,618	30,762	119,836
Decrease in provisions	(12,574)	(12,583)	(8,902)
Decrease in deferred revenue	(13,086)	(69,179)	(82,582)
Increase in plan assets	(203,420)	(224,244)	(223,194)
Payment of severance benefits	(118,391)	(121,835)	(117,691)
Cash generated from operations (1+2+3)	₩ 4,318,884	₩ 5,202,520	₩ 4,579,260

Cash Generated from Operatio185

Cash Generated from Operations - Summary of Significant Transactions not Affecting Cash Flows (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from (used in) operating activities [abstract]
Reclassification of the current portion of debentures	₩ 1,416,066	₩ 1,617,175	₩ 1,551,300
Reclassification of construction-in-progress to property, plant and equipment	2,686,591	2,212,324	2,373,023
Reclassification of accounts payable from property, plant and equipment	225,601	91,407	78,663
Reclassification of accounts payable from intangible assets	(227,108)	668,564	(170,870)
Reclassification of payable from defined benefit liability	36,209	5,746	1,675
Reclassification of payable from plan assets	₩ 43,035	₩ (9,731)	₩ 13,717

Changes in Liabilities Arisi186

Changes in Liabilities Arising from Financing Activities - Summary of Changes in Liabilities Arising from Financial Activities (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2017KRW (₩)
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	₩ 8,545,724
Cash flows	(1,307,022)
Newly aquired	68,938
Exchange difference	(167,373)
Fair value change	(25,328)
Other changes	(148,190)
Ending	6,966,749
Borrowings [Member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	8,120,791
Cash flows	(1,163,917)
Exchange difference	(221,495)
Other changes	(51,717)
Ending	6,683,662
Financial lease liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	180,714
Cash flows	(71,735)
Newly aquired	68,938
Other changes	(1,039)
Ending	176,878
Derivative assets [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	227,318
Cash flows	(71,370)
Exchange difference	(76,552)
Fair value change	2,687
Other changes	(74,694)
Ending	7,389
Derivative liabilities [member]
Disclosure of reconciliation of liabilities arising from financing activities [line items]
Beginning	16,901
Exchange difference	130,674
Fair value change	(28,015)
Other changes	(20,740)
Ending	₩ 98,820

Segment Information - Summary o

Segment Information - Summary of Segment Information (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of operating segments [Line Items]
Operating revenues	₩ 23,546,929	₩ 23,120,878	₩ 22,699,856
Operating income (loss)	1,069,092	1,339,780	1,077,068
Depreciation and Amortization	3,364,502	3,345,266	3,338,598
Operating segments [member]
Disclosure of operating segments [Line Items]
Operating revenues	27,217,843	26,699,112	26,427,216
Operating income (loss)	1,112,554	1,378,653	1,096,256
Depreciation and Amortization	3,356,126	3,337,353	3,333,984
Operating segments [member] | Marketing/Customer [member]
Disclosure of operating segments [Line Items]
Operating revenues	16,242,552	16,144,415	16,130,454
Operating income (loss)	1,018,593	1,050,053	816,679
Depreciation and Amortization	2,895,930	2,870,161	2,897,876
Operating segments [member] | Finance [member]
Disclosure of operating segments [Line Items]
Operating revenues	3,637,917	3,577,549	3,512,721
Operating income (loss)	205,678	208,566	281,477
Depreciation and Amortization	28,827	28,868	25,466
Operating segments [member] | Satellite TV [member]
Disclosure of operating segments [Line Items]
Operating revenues	685,822	668,945	668,521
Operating income (loss)	75,373	79,987	97,701
Depreciation and Amortization	99,216	98,895	95,951
Operating segments [member] | All other segments [member]
Disclosure of operating segments [Line Items]
Operating revenues	6,651,552	6,308,203	6,115,520
Operating income (loss)	(187,090)	40,047	(99,601)
Depreciation and Amortization	332,153	339,429	314,691
Elimination [member]
Disclosure of operating segments [Line Items]
Operating revenues	(3,670,914)	(3,578,234)	(3,727,360)
Operating income (loss)	(43,462)	(38,873)	(19,188)
Depreciation and Amortization	₩ 8,376	₩ 7,913	₩ 4,614

Segment Information - Summar188

Segment Information - Summary of Operating Revenues and Non Current Assets by Geographical Regions (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of geographical areas [Line Items]
Operating revenues	₩ 23,546,929	₩ 23,120,878	₩ 22,699,856
Non-current assets	17,384,554	18,482,958
Domestic [member]
Disclosure of geographical areas [Line Items]
Operating revenues	23,481,703	23,026,255	22,628,778
Non-current assets	17,246,640	18,308,310
Overseas [member]
Disclosure of geographical areas [Line Items]
Operating revenues	65,226	94,623	₩ 71,078
Non-current assets	₩ 137,914	₩ 174,648

Related Party Transactions - Su

Related Party Transactions - Summary of Related Parties Outstanding Balances of Receivables and Payables (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	₩ 2,249	₩ 1,440
Loans and receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	2,510
Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	43,369	33,298
Trade payables [member]
Disclosure of transactions between related parties [Line Items]
Payables		3
Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	7,536	55,000
KT Wibro Infra Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables		43,394
K-Realty CR-REITs No.1 [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	778	882
K-Realty CR-REITs No.1 [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	33,800	33,110
MOS GS Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	17	9
MOS GS Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables		1
MOS GS Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	392	1,494
MOS Daegu Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1	1
MOS Daegu Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	1,388	1,082
MOS Chungcheong Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1	6
MOS Chungcheong Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	290	1
MOS Chungcheong Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	1,827	2,065
MOS Gangnam Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	6	6
MOS Gangnam Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1	1
MOS Gangnam Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	287	1,129
MOS GB Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	17	19
MOS GB Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1	5
MOS GB Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	778	2,167
MOS BS Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	34	34
MOS BS Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1	1
MOS BS Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	46	1,114
MOS Honam Co., Ltd. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	2	2
MOS Honam Co., Ltd. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1
MOS Honam Co., Ltd. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	384	1,289
Others [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	54	481
Others [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1,281	179
Others [member] | Trade payables [member]
Disclosure of transactions between related parties [Line Items]
Payables		3
Others [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	2,135	₩ 1,266
K Bank Inc. [member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1,338
K Bank Inc. [member] | Other receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	7,994
K Bank Inc. [member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	296
NgeneBio [Member] | Trade receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	1
NgeneBio [Member] | Loans and receivables [member]
Disclosure of transactions between related parties [Line Items]
Receivables	2,510
NgeneBio [Member] | Other payables [member]
Disclosure of transactions between related parties [Line Items]
Payables	₩ 3

Related Party Transactions -190

Related Party Transactions - Summary of Significant Transactions with Related Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of transactions between related parties [Line Items]
Sales	₩ 37,282	₩ 8,009	₩ 30,791
Purchases	156,259	177,666	325,144
KT Service Bukbu [Member]
Disclosure of transactions between related parties [Line Items]
Sales			2,143
Purchases			28,550
Information Technology Solution Nambu Corporation [Member]
Disclosure of transactions between related parties [Line Items]
Sales			2,707
Purchases			24,025
Information Technology Solution Seobu Corporation [Member]
Disclosure of transactions between related parties [Line Items]
Sales			2,324
Purchases			20,031
Information Technology Solution Busan Corporation [Member]
Disclosure of transactions between related parties [Line Items]
Sales			1,496
Purchases			14,049
KT Service Nambu [Member]
Disclosure of transactions between related parties [Line Items]
Sales			1,972
Purchases			21,133
Information Technology Solution Honam Corporation [Member]
Disclosure of transactions between related parties [Line Items]
Sales			2,050
Purchases			29,538
Information Technology Solution Daegu Corporation [Member]
Disclosure of transactions between related parties [Line Items]
Sales			1,256
Purchases			18,272
KT Wibro Infra Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales		11	11
Purchases		391	814
Smart Channel Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Sales		766	6,545
Purchases			4,722
K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [Line Items]
Sales	2,233	1,989	2,133
Purchases	35,532	37,469	38,167
MOS GS Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	704	663	752
Purchases	16,946	17,361	17,474
MOS Daegu Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	335	291	357
Purchases	8,514	12,220	12,227
MOS Chungcheong Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	455	408	310
Purchases	15,542	13,469	12,735
MOS Gangnam Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	484	412	454
Purchases	16,380	15,797	15,829
MOS GB Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	987	891	964
Purchases	21,651	21,802	21,582
MOS BS Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	460	441	453
Purchases	15,957	15,346	15,482
MOS Honam Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Sales	493	418	470
Purchases	14,294	14,389	17,004
Others [member]
Disclosure of transactions between related parties [Line Items]
Sales	1,149	1,719	4,394
Purchases	11,384	₩ 29,422	₩ 13,510
K Bank Inc. [member]
Disclosure of transactions between related parties [Line Items]
Sales	29,939
Purchases	59
NgeneBio [Member]
Disclosure of transactions between related parties [Line Items]
Sales	₩ 43

Related Party Transactions -191

Related Party Transactions - Summary of Significant Transactions with Related Parties (Parenthetical) (Detail) ₩ in Millions	12 Months Ended
	Dec. 31, 2015KRW (₩)
KT Rental Co., Ltd. and KT Capital Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Operating income discontinued operations	₩ 6,634

Related Party Transactions -192

Related Party Transactions - Summary of Key Management Compensation (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of transactions between related parties [abstract]
Salaries and other short-term benefits	₩ 2,879	₩ 2,629	₩ 2,455
Post-employment benefits	311	381	413
Stock-based compensation	1,331	1,237	997
Total	₩ 4,521	₩ 4,247	₩ 3,865

Related Party Transactions -193

Related Party Transactions - Summary of Fund Transactions with Related Parties (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	₩ 41,851	₩ 38,675
Dividend income	6,212	7,554
KT-DSC creative economy youth start-up investment fund [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash		6,000
PT. Mitra Transaksi Indonesia [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	5,194	16,626
K-Realty rental housing REIT [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash		5,500
AI Research institute [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash		3,000
KT-IBKC future investment fund [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	7,500	3,750
Gyeonggi-KT Yoojin Superman Fund [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	1,000	1,000
FUNDA Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash		2,799
K-Realty CR-REITs No.1 [member]
Disclosure of transactions between related parties [Line Items]
Dividend income		4,186
Korea information & technology investment fund [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	739	3,201
Daiwon Broadcasting Co., Ltd. [Member]
Disclosure of transactions between related parties [Line Items]
Dividend income		85
Others [Member]
Disclosure of transactions between related parties [Line Items]
Dividend income		₩ 82
CHAMP IT Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	750
Korea Electronic Vehicle Charging Service [Member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	864
K-REALTY CR REIT [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	5,392
K Bank Inc. [member]
Disclosure of transactions between related parties [Line Items]
Equity contributions in cash	26,543
MOS GS Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	12
MOS Daegu Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	12
MOS Chungcheong Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	12
MOS Gangnam Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	10
MOS GB Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	15
MOS BS Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	10
MOS Honam Co., Ltd. [member]
Disclosure of transactions between related parties [Line Items]
Dividend income	₩ 10

Financial Risk Management - Sum

Financial Risk Management - Summary of Exposures to Risks, Effects on Profit before Income Tax and Shareholders' Equity (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
10% strengthening in foreign exchange rate [member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of foreign exchange rate	10.00%	10.00%	10.00%
Income before tax	₩ (10,132)	₩ (28,134)	₩ (52,157)
Shareholders' equity	₩ (7,273)	₩ (23,817)	₩ (45,632)
10% weakening in foreign exchange rate [member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of foreign exchange rate	(10.00%)	(10.00%)	(10.00%)
Income before tax	₩ 10,132	₩ 28,134	₩ 52,157
Shareholders' equity	₩ 7,273	₩ 23,817	₩ 45,632
Ten percentage increase in market equity price [Member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of price	10.00%	10.00%	10.00%
Shareholders' equity	₩ 686	₩ 539	₩ 3,469
10% decrease in market equity price [Member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of price	(10.00%)	(10.00%)	(10.00%)
Shareholders' equity	₩ (686)	₩ (539)	₩ (3,469)
100 basis point increase in market interest rate [Member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of interest rate	1.00%	1.00%	1.00%
Income before tax	₩ 1,942	₩ (3,456)	₩ (3,601)
Shareholders' equity	₩ 4,868	₩ (1,673)	₩ (245)
100 basis point decrease in market interest rate [Member]
Disclosure of detailed information about financial instruments [Line Items]
Fluctuation of interest rate	1.00%	1.00%	1.00%
Income before tax	₩ (1,954)	₩ 3,445	₩ 3,615
Shareholders' equity	₩ (5,198)	₩ (5,025)	₩ (5,764)

Financial Risk Management - 195

Financial Risk Management - Summary of Details of Financial Assets and Liabilities in Foreign Currencies (Detail) € in Thousands, ₫ in Thousands, ৳ in Thousands, دج in Thousands, ¥ in Thousands, ¥ in Thousands, £ in Thousands, zł in Thousands, Tsh in Thousands, SFr in Thousands, Rp in Thousands, P in Thousands, K in Thousands, FRw in Thousands, $ in Thousands, $ in Thousands, in Thousands, in Thousands, ₩ in Millions

Dec. 31, 2017KRW (₩)

Dec. 31, 2017USD ($)

Dec. 31, 2017VND (₫)

Dec. 31, 2017XDR ( )

Dec. 31, 2017BDT (৳)

Dec. 31, 2017CNY (¥)

Dec. 31, 2017EUR (€)

Dec. 31, 2017GBP (£)

Dec. 31, 2017JPY (¥)

Dec. 31, 2017PLN (zł)

Dec. 31, 2017UZS ( )

Dec. 31, 2017RWF (FRw)

Dec. 31, 2017TZS (Tsh)

Dec. 31, 2017BWP (P)

Dec. 31, 2017MMK (K)

Dec. 31, 2017IDR (Rp)

Dec. 31, 2017DZD (دج)

Dec. 31, 2017CHF (SFr)

Dec. 31, 2016KRW (₩)

Dec. 31, 2016USD ($)

Dec. 31, 2016VND (₫)

Dec. 31, 2016XDR ( )

Dec. 31, 2016BDT (৳)

Dec. 31, 2016CNY (¥)

Dec. 31, 2016EUR (€)

Dec. 31, 2016HKD ($)

Dec. 31, 2016GBP (£)

Dec. 31, 2016JPY (¥)

Dec. 31, 2016PLN (zł)

Dec. 31, 2016UZS ( )

Dec. 31, 2016RWF (FRw)

Dec. 31, 2016TZS (Tsh)

Dec. 31, 2016BWP (P)

Dec. 31, 2016MMK (K)

Dec. 31, 2016IDR (Rp)

Dec. 31, 2016DZD (دج)

Dec. 31, 2015USD ($)

Dec. 31, 2015VND (₫)

Dec. 31, 2015XDR ( )

Dec. 31, 2015BDT (৳)

Dec. 31, 2015CNY (¥)

Dec. 31, 2015EUR (€)

Dec. 31, 2015HKD ($)

Dec. 31, 2015GBP (£)

Dec. 31, 2015JPY (¥)

Dec. 31, 2015PLN (zł)

Disclosure of detailed information about financial instruments [Line Items]

Financial assets

₩ 10,237,369

₩ 10,216,182

Financial liabilities

₩ 15,295,656

₩ 16,557,537

Currency risk [Member]

Disclosure of detailed information about financial instruments [Line Items]

Financial assets

$ 236,476

₫ 311,649

306

৳ 38,074

¥ 46,555

€ 186

¥ 28,267

zł 338

136,787

FRw 3,346

Tsh 317,348

P 42

K 84

Rp 14,886,393

دج 47

$ 210,474

₫ 515,412

311

৳ 69,473

¥ 15,262

€ 40

$ 254

£ 1

¥ 80,555

zł 106,025

39,531

FRw 1,203

Tsh 29,987

P 15

K 2,750

Rp 15,646,011

دج 471

$ 183,254

₫ 270,000

444

৳ 6

¥ 15,562

€ 29

$ 9

£ 8

¥ 73,716

zł 207,273

Financial liabilities

$ 1,908,831

738

¥ 10

€ 3,625

£ 74

¥ 21,801,443

Rp 710,162

SFr 12

$ 2,536,090

737

¥ 381

€ 2,571

£ 151

¥ 21,802,051

Rp 53,142,167

$ 2,351,003

849

¥ 107

€ 29

£ 888

¥ 40,279,411

Financial Risk Management - 196

Financial Risk Management - Summary of Maximum Exposure to Credit Risk (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	₩ 10,070,273	₩ 9,975,310
Cash equivalents(except cash on hand) [Member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	1,926,620	2,875,383
Trade and other receivables [Member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	6,643,115	6,036,363
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	5,813	6,277
Derivative used for hedging [Member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	7,389	227,318
Time deposits and others [Member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	1,333,317	716,769
Available-for-sale [member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	9,899	26,684
Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	151	30,143
Financial guarantee contracts [Member]
Disclosure of detailed information about financial instruments [Line Items]
Maximum exposure to credit risk	₩ 143,969	₩ 56,373

Financial Risk Management - 197

Financial Risk Management - Summary of Contractual Undiscounted Cash Flows (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	₩ 9,262,238	₩ 9,021,467
Borrowings (including debentures)	7,607,931	9,327,424
Other non-derivative financial liabilities	12,569	26,422
Financial guarantee contracts	26,738	56,373
Total	16,909,476	18,431,686
Less than 1 year [member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	7,880,906	7,682,604
Borrowings (including debentures)	1,623,996	2,034,524
Other non-derivative financial liabilities	4,117	233
Financial guarantee contracts	26,738	56,373
Total	9,535,757	9,773,734
1-5 years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	1,219,835	1,121,452
Borrowings (including debentures)	3,666,726	4,834,151
Other non-derivative financial liabilities	8,452	3,272
Total	4,895,013	5,958,875
More than 5 years [Member]
Disclosure of maturity analysis for non-derivative financial liabilities [Line Items]
Trade and other payables	161,497	217,411
Borrowings (including debentures)	2,317,209	2,458,749
Other non-derivative financial liabilities		22,917
Total	₩ 2,478,706	₩ 2,699,077

Financial Risk Management - 198

Financial Risk Management - Summary of Cash Outflow and Inflow of Derivatives Settled Gross or Net are Undiscounted Contractual Cash Flow (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	₩ 1,711,595	₩ 2,886,867	₩ 2,512,533
Inflow	1,686,804	3,196,870	2,606,479
Less than 1 year [member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	638,171	1,174,147	335,970
Inflow	608,270	1,302,112	276,066
1-5 years [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	546,791	1,176,715	2,138,379
Inflow	568,976	1,306,199	2,284,219
More than 5 years [Member]
Disclosure of maturity analysis for derivative financial liabilities [Line Items]
Outflow	526,633	536,005	38,184
Inflow	₩ 509,558	₩ 588,559	₩ 46,194

Financial Risk Management - 199

Financial Risk Management - Summary of Debt-to-equity Ratios (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of detailed information about financial instruments [abstract]
Total liabilities	₩ 16,696,309	₩ 17,881,580
Total equity	₩ 13,049,130	₩ 12,782,718	₩ 12,156,131	₩ 11,787,557
Debt-to-equity ratio	128.00%	140.00%

Financial Risk Management - 200

Financial Risk Management - Summary of Gearing Ratios (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of detailed information about financial instruments [abstract]
Total borrowings	₩ 6,860,539	₩ 8,301,505
Less: cash and cash equivalents	(1,928,182)	(2,900,311)	₩ (2,559,464)	₩ (1,888,663)
Net debt	4,932,357	5,401,194
Total equity	13,049,130	12,782,718	₩ 12,156,131	₩ 11,787,557
Total capital	₩ 17,981,487	₩ 18,183,912
Gearing ratio	27.00%	30.00%

Financial Risk Management - 201

Financial Risk Management - Summary of Group's Recognized Financial Assets Subject to Enforceable Master Netting Arrangements or Similar Agreements (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of offsetting of financial assets [Line Items]
Gross assets	₩ 97,719	₩ 131,199
Gross liabilities offset	(5,446)
Net amounts presented in the statement of financial position	92,273	131,199
Amounts not offset, Financial instruments	(81,700)	(97,369)
Amounts not offset, Cash collateral	0	0
Net amount	10,573	33,830
Derivative liabilities for hedging purpose [Member]
Disclosure of offsetting of financial assets [Line Items]
Gross assets	3,284	35,334
Net amounts presented in the statement of financial position	3,284	35,334
Amounts not offset, Financial instruments	(3,284)	(5,707)
Amounts not offset, Cash collateral	0	0
Net amount		29,627
Trade receivables [member]
Disclosure of offsetting of financial assets [Line Items]
Gross assets	85,755	95,865
Gross liabilities offset	(5,010)
Net amounts presented in the statement of financial position	80,745	95,865
Amounts not offset, Financial instruments	(73,109)	(91,662)
Amounts not offset, Cash collateral	0	0
Net amount	7,636	₩ 4,203
Other Financial Assets1 [Member]
Disclosure of offsetting of financial assets [Line Items]
Gross assets	8,680
Gross liabilities offset	(436)
Net amounts presented in the statement of financial position	8,244
Amounts not offset, Financial instruments	(5,307)
Amounts not offset, Cash collateral	0
Net amount	₩ 2,937

Financial Risk Management - 202

Financial Risk Management - Summary of Group's Recognized Financial Liabilities Subject to Enforceable Master Netting Arrangements or Similar Agreements (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	₩ 112,513	₩ 111,110
Gross assets offset	(5,446)	(4)
Net amounts presented in the statement of financial position	107,067	111,106
Amounts not offset, Financial instruments	(81,700)	(106,811)
Amounts not offset, Cash collateral	0	0
Net amount	25,367	4,295
Derivatives used for hedging [Member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	26,135	20,627
Net amounts presented in the statement of financial position	26,135	20,627
Amounts not offset, Financial instruments	(3,284)	(20,627)
Amounts not offset, Cash collateral	0	0
Net amount	22,851
Trade payables [member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	80,829	90,435
Gross assets offset	(5,217)
Net amounts presented in the statement of financial position	75,612	90,435
Amounts not offset, Financial instruments	(73,109)	(86,184)
Amounts not offset, Cash collateral	0	0
Net amount	2,503	4,251
Other payables [member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities		48
Gross assets offset		(4)
Net amounts presented in the statement of financial position		44
Amounts not offset, Cash collateral		0
Net amount		₩ 44
Other [Member]
Disclosure of offsetting of financial liabilities [Line Items]
Gross liabilities	5,549
Gross assets offset	(229)
Net amounts presented in the statement of financial position	5,320
Amounts not offset, Financial instruments	(5,307)
Amounts not offset, Cash collateral	0
Net amount	₩ 13

Fair Value - Summary of Carryin

Fair Value - Summary of Carrying Amount and Fair Value of Financial Instruments by Category (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	₩ 10,237,369	₩ 10,216,182
Financial liabilities	15,295,656	16,557,537
Trade and other payables [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	8,425,503	8,328,082
Borrowings [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	6,683,662	8,120,791
Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	5,051	1,973
Derivative financial instruments for hedging purpose [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	93,770	14,928
Other [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	87,670	91,763
Cash and cash equivalents [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	1,928,182	2,900,311
Trade and other receivables [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	6,643,115	6,036,363
Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	5,813	6,277
Derivative financial instruments for hedging purpose [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	7,389	227,318
Time deposits and others [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	1,333,317	716,769
Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	151	30,143
Available-for-sale [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	319,402	299,001
Fair value [Member] | | Borrowings [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	6,738,326	8,184,195
Fair value [Member] | | Financial liabilities designated as at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	5,051	1,973
Fair value [Member] | | Derivative financial instruments for hedging purpose [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial liabilities	93,770	14,928
Fair value [Member] | | Financial assets at fair value through profit or loss [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	5,813	6,277
Fair value [Member] | | Derivative financial instruments for hedging purpose [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	7,389	227,318
Fair value [Member] | | Held-to-maturity financial assets [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	151	30,143
Fair value [Member] | | Available-for-sale [member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets	₩ 319,402	₩ 299,001

Fair Value - Summary of Availab

Fair Value - Summary of Available-for-sale Financial Assets Measured at Cost (Detail) - Available-for-sale [member] - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	₩ 61,551	₩ 105,773
K- Bank [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost		36,500
IBK-AUCTUS Green Growth Private Equity Fund [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	8,518	9,506
CBC II Fund [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	4,670	4,710
TRANSLINK No.2 Fund [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	9,395	9,395
WALDEN No.6 Fund [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	8,453	7,550
Storm IV Fund [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	7,298	8,601
Others [Member]
Disclosure of fair value measurement of assets [Line Items]
Available-for-sale financial assets measured at cost	₩ 23,217	₩ 29,511

Fair Value - Summary of Fair Va

Fair Value - Summary of Fair Value Hierarchy Classifications of Financial Assets and Financial Liabilities That are Measured at Fair Value (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	₩ 5,813	₩ 6,277
Associates and joint ventures	279,431	284,075
Borrowings	6,683,662	8,120,791
Derivative financial assets for hedging purpose	7,389	227,318
Investment properties	1,189,531	1,148,044	₩ 1,102,070
Available-for-sale financial assets	380,953	404,774	₩ 360,037
Financial assets	10,237,369	10,216,182
Financial assets, at fair value	2,088,204	2,499,315
Financial liabilities at fair value through profit or loss	5,051	1,973
Derivative financial liabilities for hedging purpose	93,770	14,928
Financial liabilities	15,295,656	16,557,537
Financial liabilities, at fair value	6,837,147	8,201,096
Recurring fair value measurement [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	5,813	6,277
Derivative financial assets for hedging purpose	7,389	227,318
Available-for-sale financial assets	319,402	299,001
Financial assets	332,604	532,596
Financial liabilities at fair value through profit or loss	5,051	1,973
Derivative financial liabilities for hedging purpose	93,770	14,928
Financial liabilities	98,821	16,901
Not measured at fair value in statement of financial position but for which fair value is disclosed [Member]
Disclosure of detailed information about financial instruments [Line Items]
Associates and joint ventures		3,940
Borrowings	6,738,326	8,184,195
Investment properties	1,755,600	1,962,779
Financial assets	1,755,600	1,966,719
Financial liabilities	6,738,326	8,184,195
Level 1 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets, at fair value	6,859	9,327
Level 1 [Member] | Recurring fair value measurement [Member]
Disclosure of detailed information about financial instruments [Line Items]
Available-for-sale financial assets	6,859	5,387
Financial assets	6,859	5,387
Level 1 [Member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [Member]
Disclosure of detailed information about financial instruments [Line Items]
Associates and joint ventures		3,940
Financial assets		3,940
Level 2 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets, at fair value	12,855	233,043
Financial liabilities, at fair value	76,045	14,928
Level 2 [Member] | Recurring fair value measurement [Member]
Disclosure of detailed information about financial instruments [Line Items]
Derivative financial assets for hedging purpose	7,389	227,318
Available-for-sale financial assets	5,466	5,725
Financial assets	12,855	233,043
Derivative financial liabilities for hedging purpose	76,045	14,928
Financial liabilities	76,045	14,928
Level 3 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets, at fair value	2,068,490	2,256,945
Financial liabilities, at fair value	6,761,102	8,186,168
Level 3 [Member] | Recurring fair value measurement [Member]
Disclosure of detailed information about financial instruments [Line Items]
Financial assets at fair value through profit or loss	5,813	6,277
Available-for-sale financial assets	307,077	287,889
Financial assets	312,890	294,166
Financial liabilities at fair value through profit or loss	5,051	1,973
Derivative financial liabilities for hedging purpose	17,725
Financial liabilities	22,776	1,973
Level 3 [Member] | Not measured at fair value in statement of financial position but for which fair value is disclosed [Member]
Disclosure of detailed information about financial instruments [Line Items]
Borrowings	6,738,326	8,184,195
Investment properties	1,755,600	1,962,779
Financial assets	1,755,600	1,962,779
Financial liabilities	₩ 6,738,326	₩ 8,184,195

Fair Value - Summary of Changes

Fair Value - Summary of Changes in Level 3 of Fair Value Hierarchy for Recurring Fair Value Measurements (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	₩ 30,664,298
Ending balance	29,745,439	₩ 30,664,298
Beginning balance	17,881,580
Ending balance	16,696,309	17,881,580
Recurring fair value measurement [Member] | Financial assets at fair value through profit or loss [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	6,277	18
Purchases		13,461
Amount recognized in profit or loss	(464)	(7,184)
Sales		(18)
Ending balance	5,813	6,277
Recurring fair value measurement [Member] | Available-for-sale [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	287,889	267,337
Reclassification	(277)	5,723
Amount recognized in other comprehensive income	58,450	15,099
Purchases	85,287	1,561
Amount recognized in profit or loss	(113)	(426)
Sales	(124,159)	(1,405)
Ending balance	307,077	287,889
Recurring fair value measurement [Member] | Other derivative liabilities [Member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	1,973	2,006
Reclassification	0	0
Purchases	0	0
Amount recognized in profit or loss	3,078	(33)
Sales	0	0
Ending balance	5,051	₩ 1,973
Recurring fair value measurement [Member] | Derivative financial liabilities [member] | Level 3 [Member]
Disclosure of detailed information about financial instruments [Line Items]
Reclassification	0
Amount recognized in other comprehensive income	(1,909)
Purchases	0
Amount recognized in profit or loss	19,634
Sales	0
Ending balance	₩ 17,725

Fair Value - Summary of Valuati

Fair Value - Summary of Valuation Techniques and Inputs (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other financial assets
Derivative financial assets for hedging purpose	₩ 7,389	₩ 227,318
Available-for-sale financial assets	380,953	404,774	₩ 360,037
Investment properties	1,189,531	1,148,044	₩ 1,102,070
Other financial liabilities
Derivative financial liabilities for hedging purpose	93,770	14,928
Borrowings	6,683,662	8,120,791
Recurring fair value measurement [Member]
Other financial assets
Derivative financial assets for hedging purpose	7,389	227,318
Available-for-sale financial assets	319,402	299,001
Other financial liabilities
Derivative financial liabilities for hedging purpose	93,770	14,928
Recurring fair value measurement [Member] | Level 3 [Member]
Other financial assets
Available-for-sale financial assets	307,077	287,889
Other financial liabilities
Derivative financial liabilities for hedging purpose	17,725
Recurring fair value measurement [Member] | Level 3 [Member] | Financial assets at fair value through profit or loss [member]
Other financial assets
Others	5,813	6,277
Other financial liabilities
Other derivative financial liabilities	₩ 5,051	₩ 1,973
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Discounted cash flow model Comparable Company Analysis	Discounted cash flow model Comparable Company Analysis
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Discounted cash flow model Comparable Company Analysis	Discounted cash flow model Comparable Company Analysis
Recurring fair value measurement [Member] | Level 2 [Member]
Other financial assets
Derivative financial assets for hedging purpose	₩ 7,389	₩ 227,318
Available-for-sale financial assets	5,466	5,725
Other financial liabilities
Derivative financial liabilities for hedging purpose	₩ 76,045	₩ 14,928
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques		Discounted cash flow model
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques		Discounted cash flow model
Recurring fair value measurement [Member] | Level 2, 3 [Member]
Other financial assets
Available-for-sale financial assets	₩ 312,543	₩ 293,614
Other financial liabilities
Derivative financial liabilities for hedging purpose	₩ 93,770
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Hull-White Model, Discounted cash flow model
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Hull-White Model, Discounted cash flow model
Not measured at fair value in statement of financial position but for which fair value is disclosed [Member]
Other financial assets
Investment properties	₩ 1,755,600	₩ 1,962,779
Other financial liabilities
Borrowings	6,738,326	8,184,195
Not measured at fair value in statement of financial position but for which fair value is disclosed [Member] | Level 3 [Member]
Other financial assets
Investment properties	1,755,600	1,962,779
Other financial liabilities
Borrowings	₩ 6,738,326	₩ 8,184,195
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Discounted cash flow model	Discounted cash flow model
Valuation techniques	Discounted cash flow model	Discounted cash flow model

Fair Value - Summary of Details

Fair Value - Summary of Details and Changes of Total Deferred Difference (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	₩ 10,216,182
Ending balance	10,237,369	₩ 10,216,182
Beginning balance	16,557,537
Ending balance	15,295,656	16,557,537
Other derivative liabilities [Member]
Disclosure of detailed information about financial instruments [Line Items]
New transactions	7,126
Disposal	(594)
Ending balance	6,532
Other derivatives financial assets [Member]
Disclosure of detailed information about financial instruments [Line Items]
Beginning balance	8,470	11,293
New transactions	0	0
Disposal	(2,823)	(2,823)
Ending balance	₩ 5,647	₩ 8,470

Interests in Unconsolidated 209

Interests in Unconsolidated Structured Entities - Summary of Unconsolidated Structured Entities and Nature of Risks (Detail) - KRW (₩) ₩ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of unconsolidated structured entities [Line Items]
Other financial assets	₩ 1,727,623	₩ 1,385,281
Joint ventures and Associates	279,431	284,075
Real Estate Finance [Member]
Disclosure of unconsolidated structured entities [Line Items]
Total assets of Unconsolidated Structured Entities	1,426,620	1,075,471
Other financial assets	21,800	21,932
Joint ventures and Associates	10,168	10,086
Total	31,968	32,018
Maximum loss exposure Investment Assets	31,968	32,018
PEF &Investment Fund [Member]
Disclosure of unconsolidated structured entities [Line Items]
Total assets of Unconsolidated Structured Entities	3,779,377	3,759,246
Other financial assets	52,666	60,782
Joint ventures and Associates	164,030	165,638
Total	216,696	226,420
Maximum loss exposure Investment Assets	216,696	226,420
Asset-backed Securitization [Member]
Disclosure of unconsolidated structured entities [Line Items]
Total assets of Unconsolidated Structured Entities	2,619,445	2,841,886
Unconsolidated structured entities [Member]
Disclosure of unconsolidated structured entities [Line Items]
Total assets of Unconsolidated Structured Entities	7,825,442	7,676,603
Other financial assets	74,466	82,714
Joint ventures and Associates	174,198	175,724
Total	248,664	258,438
Maximum loss exposure Investment Assets	₩ 248,664	₩ 258,438

Information About Non-contro210

Information About Non-controlling Interests - Summary of Changes in Accumulated Non-controlling Interests (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of subsidiaries [Line Items]
Accumulated non-controlling interests at the beginning of the year	₩ 1,352,844
Profit or loss allocated to non-controlling interests	84,782	₩ 86,755	₩ 78,324
Accumulated non-controlling interests at the end of the year	₩ 1,391,764	₩ 1,352,844
KT Skylife Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	49.73%	49.73%	49.73%
Accumulated non-controlling interests at the beginning of the year	₩ 329,676	₩ 316,880	₩ 297,300
Profit or loss allocated to non-controlling interests	9,395	22,445	27,032
Dividend paid to non-controlling interests	(9,817)	(8,279)	(8,325)
Others	(952)	(1,370)	873
Accumulated non-controlling interests at the end of the year	₩ 328,302	₩ 329,676	₩ 316,880
BC Card Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	30.46%	30.46%	30.46%
Accumulated non-controlling interests at the beginning of the year	₩ 329,338	₩ 322,921	₩ 292,931
Profit or loss allocated to non-controlling interests	43,961	47,068	62,943
Dividend paid to non-controlling interests	(29,490)	(44,637)	(22,650)
Others	(4,742)	3,986	(10,303)
Accumulated non-controlling interests at the end of the year	₩ 339,067	₩ 329,338	₩ 322,921
KT Powertel Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	55.15%	55.15%	55.15%
Accumulated non-controlling interests at the beginning of the year	₩ 51,751	₩ 50,926	₩ 70,231
Profit or loss allocated to non-controlling interests	1,165	112	(17,880)
Dividend paid to non-controlling interests			(1,118)
Others	137	713	(307)
Accumulated non-controlling interests at the end of the year	₩ 53,053	₩ 51,751	₩ 50,926
KT Hitel Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	32.87%	35.27%	36.30%
Accumulated non-controlling interests at the beginning of the year	₩ 51,798	₩ 50,689	₩ 51,136
Profit or loss allocated to non-controlling interests	870	1,274	(608)
Others	478	(165)	161
Accumulated non-controlling interests at the end of the year	₩ 53,146	₩ 51,798	₩ 50,689
KT Telecop Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	13.18%	13.18%	13.18%
Accumulated non-controlling interests at the beginning of the year	₩ 103,532	₩ 103,428	₩ 104,821
Profit or loss allocated to non-controlling interests	381	19	(1,000)
Others	(445)	85	(393)
Accumulated non-controlling interests at the end of the year	₩ 103,468	₩ 103,532	₩ 103,428

Information About Non-contro211

Information About Non-controlling Interests - Summary of Financial Information on Subsidiaries (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of subsidiaries [Line Items]
Current assets	₩ 9,678,243	₩ 9,716,020
Non-current assets	20,067,196	20,948,278
Current liabilities	9,458,104	9,523,137
Non-current liabilities	7,238,205	8,358,443
Equity	13,049,130	12,782,718	₩ 12,156,131	₩ 11,787,557
Accumulated non-controlling interests	1,391,764	1,352,844
Operating revenue	23,546,929	23,120,878	22,699,856
Profit or loss for the year	546,341	795,117	624,685
Total comprehensive income	478,053	789,447	555,850
The profit or loss allocated to non-controlling interests	84,782	86,755	78,324
Cash flows from operating activities	3,877,749	4,770,750	4,229,965
Cash flows from investing activities	(3,483,245)	(3,484,958)	(2,401,868)
Net (decrease)/increase in cash and cash equivalents	₩ (972,129)	₩ 340,847	₩ 670,801
KT Skylife Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	49.73%	49.73%	49.73%
Current assets	₩ 324,632	₩ 352,980	₩ 279,480
Non-current assets	468,261	424,968	431,814
Current liabilities	185,995	151,329	143,511
Non-current liabilities	24,555	80,123	74,339
Equity	582,343	546,496	493,444
Accumulated non-controlling interests	328,302	329,676	316,880	297,300
Operating revenue	687,752	668,945	668,521
Profit or loss for the year	57,314	68,863	72,987
Total comprehensive income	55,586	68,785	73,147
The profit or loss allocated to non-controlling interests	9,395	22,445	27,032
Cash flows from operating activities	99,269	155,399	157,762
Cash flows from investing activities	(81,758)	(210,480)	(92,350)
Cash flows from financing activities before dividend paid to non-controlling interests	(19,739)	(16,647)	(35,984)
Dividend paid to non-controlling interests	(9,817)	(8,279)	(8,325)
Net (decrease)/increase in cash and cash equivalents	₩ (2,228)	₩ (71,728)	₩ 29,428
BC Card Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	30.46%	30.46%	30.46%
Current assets	₩ 3,225,262	₩ 2,945,584	₩ 2,291,047
Non-current assets	823,001	705,480	672,905
Current liabilities	2,868,669	2,530,832	1,882,363
Non-current liabilities	86,369	71,571	63,271
Equity	1,093,225	1,048,661	1,018,318
Accumulated non-controlling interests	339,067	329,338	322,921	292,931
Operating revenue	3,628,995	3,567,512	3,504,946
Profit or loss for the year	156,109	163,131	218,969
Total comprehensive income	141,719	178,744	188,360
The profit or loss allocated to non-controlling interests	43,961	47,068	62,943
Cash flows from operating activities	108,203	92,818	128,927
Cash flows from investing activities	(568,518)	(37,313)	73,118
Cash flows from financing activities before dividend paid to non-controlling interests	(97,221)	(147,306)	(75,121)
Dividend paid to non-controlling interests	(29,490)	(44,637)	(22,650)
Gain or loss foreign currency translation	(184)	(178)
Net (decrease)/increase in cash and cash equivalents	₩ (557,536)	₩ (91,801)	₩ 126,924
KT Powertel Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	55.15%	55.15%	55.15%
Current assets	₩ 73,527	₩ 69,046	₩ 65,739
Non-current assets	41,598	44,679	47,776
Current liabilities	18,450	17,910	16,016
Non-current liabilities	487	1,989	5,166
Equity	96,188	93,826	92,333
Accumulated non-controlling interests	53,053	51,751	50,926	70,231
Operating revenue	69,234	81,390	104,527
Profit or loss for the year	2,112	202	(32,417)
Total comprehensive income	2,362	202	(32,417)
The profit or loss allocated to non-controlling interests	1,165	112	(17,880)
Cash flows from operating activities	13,895	7,271	(12,016)
Cash flows from investing activities	(17,354)	(8,191)	10,691
Cash flows from financing activities before dividend paid to non-controlling interests			(2,015)
Dividend paid to non-controlling interests			(1,118)
Net (decrease)/increase in cash and cash equivalents	₩ (3,459)	₩ (920)	₩ (3,340)
KT Hitel Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	32.87%	35.27%	36.30%
Current assets	₩ 150,368	₩ 158,210	₩ 157,355
Non-current assets	107,872	90,992	78,402
Current liabilities	49,922	45,277	33,656
Non-current liabilities	3,021	1,664	282
Equity	205,297	202,261	201,819
Accumulated non-controlling interests	53,146	51,798	50,689	51,136
Operating revenue	227,884	198,994	162,155
Profit or loss for the year	3,225	4,298	7,258
Total comprehensive income	3,036	1,399	6,769
The profit or loss allocated to non-controlling interests	870	1,274	(608)
Cash flows from operating activities	28,320	28,987	22,556
Cash flows from investing activities	(36,086)	(33,238)	(19,949)
Gain or loss foreign currency translation	(47)	3
Net (decrease)/increase in cash and cash equivalents	₩ (7,766)	₩ (4,251)	₩ 2,607
KT Telecop Co., Ltd. [member]
Disclosure of subsidiaries [Line Items]
Non-controlling Interests rate(%)	13.18%	13.18%	13.18%
Current assets	₩ 73,023	₩ 63,802	₩ 58,457
Non-current assets	191,330	201,751	210,734
Current liabilities	90,569	53,903	82,353
Non-current liabilities	41,064	78,441	52,613
Equity	132,720	133,209	134,225
Accumulated non-controlling interests	103,468	103,532	103,428	₩ 104,821
Operating revenue	317,591	315,948	302,844
Profit or loss for the year	2,885	143	(7,593)
Total comprehensive income	(490)	143	(7,593)
The profit or loss allocated to non-controlling interests	381	19	(1,000)
Cash flows from operating activities	57,262	60,461	36,216
Cash flows from investing activities	(43,483)	(45,243)	(91,846)
Cash flows from financing activities before dividend paid to non-controlling interests			(32,491)
Net (decrease)/increase in cash and cash equivalents	₩ 13,779	₩ 15,218	₩ (88,121)

Information About Non-contro212

Information About Non-controlling Interests - Summary of Changes in Ownership Interest on the Equity Attributable to Owners (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of subsidiaries [abstract]
Carrying amount of non-controlling interests acquired	₩ (732)	₩ 4,022
Consideration paid to non-controlling interests	6,173	7,347	₩ 2,699
Excess of consideration paid recognized in parent's equity	₩ 5,441	₩ 11,369	₩ 2,699

Events After Reporting Period -

Events After Reporting Period - Additional Information (Detail) - Major business combination [member] - SG Safety Corporation [member] ₩ in Millions	Apr. 09, 2018KRW (₩)
Disclosure of non-adjusting events after reporting period [line items]
Consideration	₩ 28,000
Acquisition date	May 31, 2018

Events after Reporting Perio214

Events after Reporting Period - Summary of Public Bonds Issued After Reporting Period (Detail) - Gross carrying amount [member] ₩ in Millions	12 Months Ended
	Dec. 31, 2017KRW (₩)
The 190-1st Public bond January twenty nine, twenty twenty one [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	2018.01.30
Carrying amount	₩ 110,000
Interest rate	2.55%
Redemption date	2021.01.29
The 190-2nd Public bond, January thirty, twenty twenty three [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	2018.01.30
Carrying amount	₩ 150,000
Interest rate	2.75%
Redemption date	2023.01.30
The 190-3rd Public bond, January thirty, twenty twenty eight [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	2018.01.30
Carrying amount	₩ 170,000
Interest rate	2.95%
Redemption date	2028.01.30
The 190-4th Public bond, January thirty, twenty thirty eight [member]
Disclosure of non-adjusting events after reporting period [line items]
Issue date	2018.01.30
Carrying amount	₩ 70,000
Interest rate	2.93%
Redemption date	2038.01.30