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FINANCIAL INSTRUMENTS - Net investment hedge (Details) R$ in Thousands, $ in Billions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 BRL (R$) | Dec. 31, 2017 BRL (R$) | Dec. 31, 2016 BRL (R$) | Dec. 31, 2018 USD ($)
Net investment hedge |  |  |  |
Unrealized gain (loss) on net investment hedge, net of tax | R$ | R$ (1,491,534) | R$ (148,560) | R$ 1,679,312 |
Ten/Thirty Years Bonds |  |  |  |
Net investment hedge |  |  |  |
Liabilities (not designated as hedges) at fair value through income statement |  |  |  | $ 0.3
Ten/Thirty Years Bonds | Hedges of net investment in foreign operations |  |  |  |
Net investment hedge |  |  |  |
Hedging instrument, liabilities |  |  |  | 1.8
Unrealized gain (loss) on net investment hedge, net of tax | R$ | R$ 1,491,534 | R$ 148,560 |  |
Ten/Thirty Years Bonds | Gerdau Acominas S.A. and subsidiary | Hedges of net investment in foreign operations |  |  |  |
Net investment hedge |  |  |  |
Hedging instrument, liabilities |  |  |  | $ 0.1

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- Definition The amount of financial liabilities that meet either of the following conditions: (a) they meet the definition of held for trading; or (b) upon initial recognition they are designated by the entity as at fair value through profit or loss. An entity may use this designation only when permitted by paragraph 4.3.5 of IFRS 9 (embedded derivatives) or when doing so results in more relevant information, because either: (a) it eliminates or significantly reduces a measurement or recognition inconsistency (sometimes referred to as ‘an accounting mismatch’) that would otherwise arise from measuring assets or liabilities or recognising the gains and losses on them on different bases; or (b) a group of financial liabilities or financial assets and financial liabilities is managed and its performance is evaluated on a fair value basis, in accordance with a documented risk management or investment strategy, and information about the group is provided internally on that basis to the entity’s key management personnel (as defined in IAS 24). [Refer: At fair value [member]; Key management personnel of entity or parent [member]; Derivatives [member]; Financial assets; Financial liabilities] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 8 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_8_e&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The gains (losses) recognised in other comprehensive income on hedges of net investments in foreign operations, net of tax. [Refer: Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 39 -IssueDate 2018-01-01 -Paragraph 102 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=39&date=2018-03-01&anchor=para_102_a&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 24C -Subparagraph b -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_24C_b_i&doctype=Standard -URIDate 2018-03-16 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 24E -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_24E_a&doctype=Standard -URIDate 2018-03-16 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_91_a&doctype=Standard -URIDate 2018-03-16 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 9 -IssueDate 2018-01-01 -Paragraph 6.5.13 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=9&date=2018-03-01&anchor=para_6.5.13_a&doctype=Standard -URIDate 2018-03-16 + Details
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