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Deferred Income Tax and Income Tax Expense - Summary of Tax Impacts Recognized Directly To Equity (Detail) - KRW (₩) ₩ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Deferred tax assets and liabilities [abstract] |  |  |
Gain on valuation of financial assets at fair value through other comprehensive income, Before recognition | ₩ 54,969 | ₩ 225,635 | ₩ 59,384
Gain (loss) on valuation of hedge instruments (loss)liabilities, Before recognition | 37,247 | 31,003 | (36,756)
Remeasurements of net defined benefit liabilities, Before recognition | (77,382) | (33,814) | (116,324)
Share of Gain (loss) of associates and joint ventures, and others, Before recognition | 25,538 | 4,493 | (1,036)
Exchange differences on translation for foreign operations, Before recognition | (3,614) | 6,692 | 3,989
Total, Before recognition | 36,758 | 234,009 | (90,743)
Gain on valuation of financial assets at fair value through other comprehensive income, Tax effect | (12,972) | (58,483) | (15,573)
Gain (loss) on valuation of hedge instruments (loss)liabilities, Tax effect | (9,860) | (8,139) | 9,745
Remeasurements of net defined benefit liabilities, Tax effect | 17,201 | 8,037 | 42,813
Share of Gain (loss) of associates and joint ventures, and others, Tax effect | (8,820) | (1,327) | 179
Exchange differences on translation for foreign operations, Tax effect | 948 | (1,759) | (1,049)
Total, Tax effect | 77,103 | (61,669) | 36,115
Gain on valuation of financial assets at fair value through other comprehensive income, After recognition | 41,997 | 167,152 | 43,811
Gain (loss) on valuation of hedge instruments (loss)liabilities, After recognition | 27,387 | 22,864 | (27,011)
Remeasurements of net defined benefit liabilities, After recognition | (60,181) | (25,777) | (73,511)
Share of Gain (loss) of associates and joint ventures, and others, After recognition | 16,718 | 3,166 | (857)
Exchange differences on translation for foreign operations, After recognition | (2,666) | 4,933 | 2,940
Total other comprehensive income (loss) | ₩ 23,255 | ₩ 172,338 | ₩ (54,628)

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- Definition The gains (losses) recognised in other comprehensive income on financial assets measured at fair value through other comprehensive income, before tax. [Refer: Financial assets measured at fair value through other comprehensive income; Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2020-01-01 -Paragraph 20 -Subparagraph a -Clause viii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2020-en-r&anchor=para_20_a_viii&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_b&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The gains (losses) recognised in other comprehensive income on financial assets measured at fair value through other comprehensive income, net of tax. [Refer: Financial assets measured at fair value through other comprehensive income; Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_a&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to amounts recognised in other comprehensive income in relation to cash flow hedges. [Refer: Cash flow hedges [member]; Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2020-01-01 -Paragraph 81 -Subparagraph ab -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_ab&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 90 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_90&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to amounts recognised in other comprehensive income. [Refer: Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2020-01-01 -Paragraph 81 -Subparagraph ab -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_ab&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 90 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_90&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to amounts recognised in other comprehensive income in relation to exchange differences on the translation of financial statements of foreign operations. [Refer: Other comprehensive income; Reserve of exchange differences on translation] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2020-01-01 -Paragraph 81 -Subparagraph ab -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_ab&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 90 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_90&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to amounts recognised in other comprehensive income in relation to financial assets measured at fair value through other comprehensive income. [Refer: Financial assets measured at fair value through other comprehensive income; Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2020-01-01 -Paragraph 81 -Subparagraph ab -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_ab&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 90 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_90&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to amounts recognised in other comprehensive income in relation to remeasurements of defined benefit plans. [Refer: Other comprehensive income; Reserve of remeasurements of defined benefit plans; Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2020-01-01 -Paragraph 81 -Subparagraph ab -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_ab&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 90 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_90&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income tax relating to an entity's share of other comprehensive income of associates and joint ventures accounted for using the equity method that will be reclassified to profit or loss. [Refer: Share of other comprehensive income of associates and joint ventures accounted for using equity method, before tax] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of income and expense (including reclassification adjustments) that is not recognised in profit or loss as required or permitted by IFRSs. [Refer: IFRSs [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 106 -Subparagraph d -Clause ii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_106_d_ii&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2020-01-01 -Paragraph B12 -Subparagraph b -Clause viii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B12_b_viii&doctype=Appendix&subtype=B -URIDate 2020-01-01 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 81A -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_81A_b&doctype=Standard -URIDate 2020-01-01 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_a&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of other comprehensive income, before tax, related to cash flow hedges. [Refer: Cash flow hedges [member]; Other comprehensive income, before tax] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_b&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 7 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_7&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of other comprehensive income, before tax, related to exchange differences on translation of financial statements of foreign operations. [Refer: Other comprehensive income, before tax] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_b&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 7 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_7&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of other comprehensive income, net of tax, related to cash flow hedges. [Refer: Cash flow hedges [member]; Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_a&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 7 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_7&doctype=Standard -URIDate 2020-01-01 + Details
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