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Borrowings - Summary of Repayment of Borrowings Including the Current Liabilities (Detail) - KRW (₩) ₩ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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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 |

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