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Changes in Accounting Policies - Summary of Effects Resulting from Classification and Measurement of Financial Instruments (Detail) - KRW (₩) ₩ in Millions | Dec. 31, 2018 | Jan. 01, 2018 | Dec. 31, 2017 | Jan. 01, 2017 | Dec. 31, 2016 | Dec. 31, 2015
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Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Cash and cash equivalent | ₩ 2,703,422 |  | ₩ 1,928,182 | ₩ 2,900,311 | ₩ 2,900,311 | ₩ 2,559,464
Trade and other receivables | 6,523,344 |  | 6,793,397 |  |  |
Other financial assets | 1,617,956 |  | 1,727,623 |  |  |
Trade payables and payables | 8,521,379 |  | 8,427,457 |  |  |
Borrowing | 6,648,293 |  | 6,683,662 |  |  |
Other financial liabilities | ₩ 164,396 |  | ₩ 186,491 |  |  |
Loans and receivables under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Trade and other receivables |  | ₩ (1,028) |  |  |  |
Other financial assets |  | (789) |  |  |  |
Loans and receivables under IAS 39 reclassified to financial assets at fair value through other comprehensive income under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Trade and other receivables |  | 24,486 |  |  |  |
Financial assets available -for- sale under IAS 39 reclassified to financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 32,745 |  |  |  |
Financial assets available -for- sale under IAS 39 reclassified to financial assets at fair value through other comprehensive income under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 2,085 |  |  |  |
Other financial liabilities measured at amortized cost under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial liabilities |  | 287 |  |  |  |
IAS 39 [member] | Loans and receivables under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Cash and cash equivalent |  | 1,928,182 |  |  |  |
Trade and other receivables |  | 6,793,397 |  |  |  |
Other financial assets |  | 1,333,317 |  |  |  |
IAS 39 [member] | Financial assets at fair value through profit or loss under IAS 39 reclassified to Financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 5,813 |  |  |  |
IAS 39 [member] | Derivative financial assets for hedging purpose under IAS 39 reclassified to Derivative financial assets for hedging purpose under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 7,389 |  |  |  |
IAS 39 [member] | Financial assets available -for- sale under IAS 39 reclassified to financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 380,953 |  |  |  |
IAS 39 [member] | Financial assets held to maturity under IAS 39 reclassified to Financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 151 |  |  |  |
IAS 39 [member] | Other financial liabilities measured at amortized cost under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Trade payables and payables |  | 8,427,457 |  |  |  |
Borrowing |  | 6,683,662 |  |  |  |
Other financial liabilities |  | 89,104 |  |  |  |
IAS 39 [member] | Financial liabilities at fair value through profit or loss under IAS 39 reclassified to financial liabilities at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial liabilities |  | 5,051 |  |  |  |
IAS 39 [member] | Derivative financial liabilities for hedging purpose under IAS 39 reclassified to derivative financial liabilities for hedging purpose under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial liabilities |  | 93,770 |  |  |  |
IFRS9 [member] | Loans and receivables under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Cash and cash equivalent |  | 1,928,182 |  |  |  |
Trade and other receivables |  | 5,836,089 |  |  |  |
Other financial assets |  | 462,075 |  |  |  |
IFRS9 [member] | Loans and receivables under IAS 39 reclassified to financial assets at fair value through other comprehensive income under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Trade and other receivables |  | 980,766 |  |  |  |
IFRS9 [member] | Loans and receivables under IAS 39 reclassified to financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 870,453 |  |  |  |
IFRS9 [member] | Financial assets at fair value through profit or loss under IAS 39 reclassified to Financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 5,813 |  |  |  |
IFRS9 [member] | Derivative financial assets for hedging purpose under IAS 39 reclassified to Derivative financial assets for hedging purpose under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 7,389 |  |  |  |
IFRS9 [member] | Financial assets available -for- sale under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 28,603 |  |  |  |
IFRS9 [member] | Financial assets available -for- sale under IAS 39 reclassified to financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 127,276 |  |  |  |
IFRS9 [member] | Financial assets available -for- sale under IAS 39 reclassified to financial assets at fair value through other comprehensive income under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 259,904 |  |  |  |
IFRS9 [member] | Financial assets held to maturity under IAS 39 reclassified to Financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 51 |  |  |  |
IFRS9 [member] | Financial assets held to maturity under IAS 39 reclassified to Financial assets at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial assets |  | 100 |  |  |  |
IFRS9 [member] | Other financial liabilities measured at amortized cost under IAS 39 reclassified to financial assets measured at amortized cost under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Trade payables and payables |  | 8,427,457 |  |  |  |
Borrowing |  | 6,683,662 |  |  |  |
Other financial liabilities |  | 89,391 |  |  |  |
IFRS9 [member] | Financial liabilities at fair value through profit or loss under IAS 39 reclassified to financial liabilities at fair value through profit or loss under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial liabilities |  | 5,051 |  |  |  |
IFRS9 [member] | Derivative financial liabilities for hedging purpose under IAS 39 reclassified to derivative financial liabilities for hedging purpose under IFRS 9 [member] |  |  |  |  |  |
Disclosure of expected impact of initial application of new standards or interpretations [line items] |  |  |  |  |  |
Other financial liabilities |  | ₩ 93,770 |  |  |  |

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