XML 115 R92.htm IDEA: XBRL DOCUMENT
v3.21.1

GOODWILL - Goodwill by segment (Details) - BRL (R$) R$ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | --- | ---
Goodwill by segment |  |  |  |
Goodwill | R$ 12,103,519 | R$ 9,469,311 | R$ 9,112,390 | R$ 7,891,142
Brazil |  |  |  |
Goodwill by segment |  |  |  |
Goodwill | 373,135 | 373,135 | 373,135 |
Special Steel |  |  |  |
Goodwill by segment |  |  |  |
Goodwill | 3,828,841 | 2,969,752 | 2,854,888 |
North America |  |  |  |
Goodwill by segment |  |  |  |
Goodwill | R$ 7,901,543 | R$ 6,126,424 | R$ 5,884,367 |

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_DisclosureOfReconciliationOfChangesInGoodwillLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 3 -IssueDate 2020-01-01 -Paragraph B67 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2020-en-r&anchor=para_B67_d&doctype=Appendix&subtype=B -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 134 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_134_a&doctype=Standard -URIDate 2020-01-01 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 36 -IssueDate 2020-01-01 -Paragraph 135 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=36&code=ifrs-tx-2020-en-r&anchor=para_135_a&doctype=Standard -URIDate 2020-01-01 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 54 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_54_c&doctype=Standard -URIDate 2020-01-01 + Details
Name: | ifrs-full_Goodwill
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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