XML 186 R163.htm IDEA: XBRL DOCUMENT
v3.21.1

IMPAIRMENT OF ASSETS (Details) R$ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 BRL (R$) segment | Dec. 31, 2019 BRL (R$) | Dec. 31, 2018 BRL (R$)
Impairment of assets |  |  |
Impairment of property, plant and equipment | R$ 411,925 | R$ 0 | R$ 0
Impairment of goodwill | R$ 0 | R$ 0 | R$ 0
Number of operating segments | segment | 4 |  |
Period for projecting the cash flows for the goodwill impairment test | P5Y |  |
Discount rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, percent of increase | 0.50% | 0.50% |
Perpetuity growth rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, percent of decrease | 0.50% | 0.50% |
North America |  |  |
Impairment of assets |  |  |
Impairment of property, plant and equipment | R$ 342,355 |  |
Perpetuity growth rate | 3.00% | 3.00% |
Pre-tax discount rate | 8.25% | 10.00% |
Amount by which unit's recoverable amount is (below) exceeds its carrying value | R$ 6,202,000 | R$ 2,690,000 |
North America | Discount rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | 4,589,000 | 1,884,000 |
North America | Perpetuity growth rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | 4,914,000 | R$ 2,098,000 |
Special Steel |  |  |
Impairment of assets |  |  |
Impairment of property, plant and equipment | R$ 69,570 |  |
Perpetuity growth rate | 3.00% | 3.00% |
Pre-tax discount rate | 8.75% | 10.50% |
Amount by which unit's recoverable amount is (below) exceeds its carrying value | R$ 2,509,000 | R$ 2,813,000 |
Special Steel | Discount rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | 1,568,000 | 2,207,000 |
Special Steel | Perpetuity growth rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | R$ 1,754,000 | R$ 2,369,000 |
South America |  |  |
Impairment of assets |  |  |
Perpetuity growth rate | 3.00% | 3.00% |
Pre-tax discount rate | 11.25% | 14.25% |
Amount by which unit's recoverable amount is (below) exceeds its carrying value | R$ 4,141,000 | R$ 521,000 |
South America | Discount rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | 3,757,000 | 414,000 |
South America | Perpetuity growth rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | R$ 3,867,000 | R$ 455,000 |
Brazil |  |  |
Impairment of assets |  |  |
Perpetuity growth rate | 3.00% | 3.00% |
Pre-tax discount rate | 9.75% | 11.25% |
Amount by which unit's recoverable amount is (below) exceeds its carrying value | R$ 13,424,000 | R$ 4,015,000 |
Brazil | Discount rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | 11,348,000 | 2,810,000 |
Brazil | Perpetuity growth rate |  |  |
Impairment of assets |  |  |
Sensitivity analysis, amount above (below) book value | R$ 11,809,000 | R$ 3,115,000 |

X
- Definition The amount by which a cash-generating unit's (group of units') recoverable amount is (below) or exceeds its carrying amount. + References No definition available. + Details
Name: | ggb_AmountByWhichUnitSRecoverableAmountIsBelowOrExceedsItsCarryingAmount
Namespace Prefix: | ggb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
Name: | ggb_IfrsNumberOfOperatingSegments
Namespace Prefix: | ggb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition In a sensitivity analysis, the amount above (below) book value attributable to a change in rates used to estimate present value. + References No definition available. + Details
Name: | ggb_SensitivityAnalysisAmountAboveBelowBookValueAttributableToChangeInRateUsedToEstimatePresentValue
Namespace Prefix: | ggb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition In a sensitivity analysis, the percentage of appreciation of rate used in estimating present value. + References No definition available. + Details
Name: | ggb_SensitivityAnalysisPercentageAppreciation
Namespace Prefix: | ggb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition In a sensitivity analysis, the percentage of depreciation of rate used in estimating present value. + References No definition available. + Details
Name: | ggb_SensitivityAnalysisPercentageDepreciation
Namespace Prefix: | ggb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The discount rate applied to cash flow projections for a cash-generating unit (group of units). [Refer: Cash-generating units [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph d -Clause v -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_d_v&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph e -Clause v -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_e_v&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_DescriptionOfDiscountRatesAppliedToCashFlowProjections
Namespace Prefix: | ifrs-full_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The growth rate used to extrapolate cash flow projections beyond the period covered by the most recent budgets/forecasts for a cash-generating unit (group of units). [Refer: Cash-generating units [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph d -Clause iv -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_d_iv&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph e -Clause iv -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_e_iv&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_DescriptionOfGrowthRateUsedToExtrapolateCashFlowProjections
Namespace Prefix: | ifrs-full_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfImpairmentLossAndReversalOfImpairmentLossLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The explanation of the period over which management has projected cash flows based on financial budgets/forecasts approved by management including, when a period greater than five years is used for a cash-generating unit (group of units), an explanation of why that longer period is justified. [Refer: Cash-generating units [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph d -Clause iii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_d_iii&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph e -Clause iii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_e_iii&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_ExplanationOfPeriodOverWhichManagementHasProjectedCashFlows
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of impairment loss recognised in profit or loss for goodwill. [Refer: Impairment loss recognised in profit or loss; Goodwill] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 3 -IssueDate 2020-01-01 -Paragraph B67 -Subparagraph d -Clause v -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2020-en-r&anchor=para_B67_d_v&doctype=Appendix&subtype=B -URIDate 2020-01-01 + Details
Name: | ifrs-full_ImpairmentLossRecognisedInProfitOrLossGoodwill
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of impairment loss recognised in profit or loss for property, plant and equipment. [Refer: Impairment loss recognised in profit or loss; Property, plant and equipment] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 16 -IssueDate 2020-01-01 -Paragraph 73 -Subparagraph e -Clause v -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=16&code=ifrs-tx-2020-en-r&anchor=para_73_e_v&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 98 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_98_a&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_ImpairmentLossRecognisedInProfitOrLossPropertyPlantAndEquipment
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfDiscountRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=ggb_PerpetuityGrowthRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_SegmentsAxis=ggb_NorthAmericaSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_SegmentsAxis=ggb_SpecialSteelSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_SegmentsAxis=ggb_SouthAmericaSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_SegmentsAxis=ggb_BrazilSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |