XML 129 R106.htm IDEA: XBRL DOCUMENT
v3.19.1

FINANCIAL INSTRUMENTS - Prospective and retrospective tests (Details) - BRL (R$) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Unrealized gains on financial instruments |  |  |
Current assets | R$ 30,711 |  |
Non-current assets | 2,706 |  |
Unrealized losses on financial instruments |  |  |
Current liabilities | (5,245) |  |
Non-current liabilities |  | R$ (1,267) |
Net Income |  |  |
Gains on financial instruments | 49,576 | 9,666 |
Losses on financial instruments | (17,484) | (19,107) |
Gains (losses) on financial instruments recognized in Net Income | 32,092 | (9,441) | R$ (38,930)
Other comprehensive income |  |  |
Gains (Losses) on financial instruments | 11,947 | (11,364) | R$ 212
Gains (Losses) on financial instruments recognized in other comprehensive income | 11,947 | (11,364) |
Unrealized gains on financial instruments |  |  |
Unrealized gains on financial instruments |  |  |
Current assets | 30,711 |  |
Non-current assets | 2,706 |  |
Unrealized gains on financial instruments | 33,417 |  |
Unrealized losses on financial instruments |  |  |
Unrealized losses on financial instruments |  |  |
Current liabilities | R$ (5,245) |  |
Non-current liabilities |  | (1,267) |
Unrealized losses on financial instruments |  | R$ (1,267) |

X
- References No definition available. + Details
Name: | ggb_UnrealizedGainsOnFinancialInstrumentsAbstract
Namespace Prefix: | ggb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | ggb_UnrealizedLossesOnFinancialInstrumentsAbstract
Namespace Prefix: | ggb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of current derivative financial assets. [Refer: Derivative financial assets] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_CurrentDerivativeFinancialAssets
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of current derivative financial liabilities. [Refer: Derivative financial liabilities] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_CurrentDerivativeFinancialLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_DerivativeFinancialAssets
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of financial liabilities classified as derivative instruments. [Refer: Financial assets; Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_DerivativeFinancialLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | ifrs-full_FinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The gains (losses) recognised in other comprehensive income on cash flow hedges, net of tax. [Refer: Cash flow hedges [member]] + References Reference 1: 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 2: 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 3: 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 4: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_23_c&doctype=Standard&book=b -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainsLossesOnCashFlowHedgesNetOfTax
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The gains (losses) resulting from change in the fair value of derivatives recognised in profit or loss. [Refer: Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_85&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainsLossesOnChangeInFairValueOfDerivatives
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | ifrs-full_GainsLossesOnChangeInFairValueOfDerivativesAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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 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 + Details
Name: | ifrs-full_GainsLossesOnFinancialAssetsMeasuredAtFairValueThroughOtherComprehensiveIncomeNetOfTax
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The gains resulting from change in the fair value of derivatives recognised in profit or loss. [Refer: Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_85&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainsOnChangeInFairValueOfDerivatives
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The losses resulting from changes in the fair value of derivatives recognised in profit or loss. [Refer: Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_85&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_LossesOnChangeInFairValueOfDerivatives
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of non-current derivative financial assets. [Refer: Derivative financial assets] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_NoncurrentDerivativeFinancialAssets
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of non-current derivative financial liabilities. [Refer: Derivative financial liabilities] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_NoncurrentDerivativeFinancialLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ggb_UnrealizedGainsOnFinancialInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ggb_UnrealizedLossesOnFinancialInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |