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RELATED-PARTY TRANSACTIONS - Operations with related parties, guarantees granted (Details) - Financing Agreements - BRL (R$) R$ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Joint-venture | Diaco S.A. |  |  |
Guarantees granted |  |  |
Original Amount | R$ 137,700 |  |
Carrying Amount |  |  | R$ 128,019
Joint-venture | Gerdau Corsa S.A.P.I de C.V. |  |  |
Guarantees granted |  |  |
Original Amount | 1,750,249 |  |
Carrying Amount | 1,784,868 | R$ 1,933,929 | 1,797,856
Joint-venture | Gerdau Summit Aos Fundidos e Forjados S.A. |  |  |
Guarantees granted |  |  |
Original Amount | 130,164 |  |
Carrying Amount | 37,285 | 41,571 | 6,550
Subsidiary and Joint-venture | Gerdau Metaldom S.A; Aceros Corsa S.A De C.V |  |  |
Guarantees granted |  |  |
Original Amount | 274,560 |  |
Carrying Amount | R$ 241,842 | R$ 198,619 | R$ 178,200

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- Definition The amount of outstanding commitments made by the entity in related party transactions. [Refer: Related parties [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 24 -IssueDate 2019-01-01 -Paragraph 18 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2019-en-r&anchor=para_18_b&doctype=Standard -URIDate 2019-03-27 + Details
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