XML 120 R98.htm IDEA: XBRL DOCUMENT
v3.8.0.1

DEBENTURES - Summary (Details) R$ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 BRL (R$) instrument | Dec. 31, 2016 BRL (R$)
DEBENTURES |  |
Total Debentures | R$ | R$ 47,928 | R$ 165,423
Non-current debentures | R$ | R$ 47,928 | 165,423
3rd- A and B |  |
DEBENTURES |  |
Quantity Issued | 144,000 |
Quantity Held in treasury | 136,259 |
Total Debentures | R$ | R$ 21,377 | 44,292
7th |  |
DEBENTURES |  |
Quantity Issued | 68,400 |
Quantity Held in treasury | 63,587 |
Total Debentures | R$ | R$ 1,333 | 35,942
8th |  |
DEBENTURES |  |
Quantity Issued | 179,964 |
Quantity Held in treasury | 168,242 |
Total Debentures | R$ | R$ 14,557 | 57,191
9th |  |
DEBENTURES |  |
Quantity Issued | 125,640 |
Quantity Held in treasury | 124,203 |
Total Debentures | R$ | R$ 4,900 | 10,731
11th - A and B |  |
DEBENTURES |  |
Quantity Issued | 150,000 |
Quantity Held in treasury | 147,561 |
Total Debentures | R$ | R$ 5,761 | R$ 17,267
14th |  |
DEBENTURES |  |
Quantity Issued | 20,000 |
Quantity Held in treasury | 10,174 |

X
- Definition The number of debentures held in treasury. + References No definition available. + Details
Name: | ggb_DebenturesNumberHeldInTreasury
Namespace Prefix: | ggb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of debentures issued. + References No definition available. + Details
Name: | ggb_DebenturesNumberIssued
Namespace Prefix: | ggb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition The non-current portion of non-current notes and debentures issued. [Refer: Notes and debentures issued] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_NoncurrentPortionOfNoncurrentNotesAndDebenturesIssued
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The amount of notes and debentures issued by the entity. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_NotesAndDebenturesIssued
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceThirdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceSeventhMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceEighthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceNinthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceEleventhMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_BorrowingsByNameAxis=ggb_DebenturesIssuanceFourteenthMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |