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OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS (Details) - BRL (R$) R$ in Thousands | Jul. 14, 2015 | Dec. 31, 2018 | Dec. 31, 2017
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OBLIGATIONS WITH FIDC - INVESTMENT FUND IN CREDIT RIGHTS |  |  |
Non standardized credit right investment, fair value at inception date | R$ 800,000 |  |
Obligations with FIDC |  | R$ 938,526 | R$ 1,135,077

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- Definition Fair value of non standardized credit right investment fund at inception date. + References No definition available. + Details
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Balance Type: | debit
Period Type: | duration

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- Definition Noncurrent portion of amount payable regarding repurchase receivables from the Credit Right Investment Fund. + References No definition available. + Details
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Namespace Prefix: | ggb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition NA. + References No definition available. + Details
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