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1. DESCRIPTION OF BUSINESS (Details Narrative) R$ in Thousands | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jul. 31, 2019 BRL (R$) | Apr. 30, 2019 BRL (R$) | Feb. 28, 2018 BRL (R$) | Dec. 31, 2020 BRL (R$) | Dec. 31, 2019 BRL (R$) Numnber MillionsTons | Dec. 31, 2018 BRL (R$) | Dec. 31, 2017 BRL (R$) | Dec. 31, 2016 BRL (R$) | Dec. 31, 2015 BRL (R$) | Sep. 30, 2019 BRL (R$)
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Number of operating activities | Numnber |  |  |  |  | 5 |  |  |  |  |
Amortization of loans and financing |  |  |  |  | R$ 138,000 |  |  |  |  |
Repayments of borrowings |  |  |  |  | 11,775,093 | R$ 5,019,978 | R$ 1,528,023 |  |  |
Caixa Economica Federal [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Repayments of borrowings |  |  |  |  |  |  |  |  | R$ 2,500,000 |
Borrowings, maturity |  |  |  |  |  |  |  |  | Maturities from 2016 and 2017 to 2018 through 2022. |
Banco do Brasil S.A [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Repayments of borrowings |  |  |  |  |  |  |  |  | R$ 2,200,000 |
Face amount |  |  | R$ 4,980,000 |  |  |  |  |  |  |
Borrowings, maturity |  |  | Maturity dates from 2018 to 2022 for maturities up to 2024. |  |  |  |  |  | Maturities from 2016 and 2017 to 2018 through 2022. |
Bradesco [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Repayments of borrowings |  |  |  |  |  |  |  | R$ 100,000 |  |
Borrowings, maturity |  |  |  |  |  |  |  | Maturities from 2016 to 2019. |  |
Bradesco [Member] | United States of America, Dollars |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  |  |  |  |  | R$ 66,000 |  |
CSN Resources S.A. [Member] | United States of America, Dollars |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Face amount | R$ 175,000 | R$ 1,000,000 | R$ 350,000 |  |  |  |  |  |  |
Borrowings, maturity | 2023 |  | Maturity date in 2023. |  |  |  |  |  |  |
CSN Resources S.A. [Member] | United States of America, Dollars | Due On 2023 [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Face amount |  | R$ 400,000 |  |  |  |  |  |  |  |
Borrowings, maturity |  | 2023 |  |  |  |  |  |  |  |
CSN Resources S.A. [Member] | United States of America, Dollars | Due On 2026 [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Face amount |  | R$ 600,000 |  |  |  |  |  |  |  |
Borrowings, maturity |  | 2026 |  |  |  |  |  |  |  |
CSN Resources S.A. [Member] | United States of America, Dollars | Tender Offer [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Repayments of borrowings |  | R$ 1,000,000 |  |  |  |  |  |  |  |
Face amount |  |  | R$ 350,000 |  |  |  |  |  |  |
Borrowings, maturity |  | Maturities scheduled for September 2019 and July 2020, respectively. | Maturities scheduled for 2019 and 2020. |  |  |  |  |  |  |
CSN Islands XI Corp [Member] | United States of America, Dollars |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Face amount |  |  |  |  |  |  |  |  |  | R$ 142,000
Events After Reporting Period [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Amortization of loans and financing |  |  |  | R$ 65,000,000 |  |  |  |  |  |
Mining Property [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Investments on mining |  |  |  |  | R$ 250,000 |  |  |  |  |
Cement [Member] |  |  |  |  |  |  |  |  |  |
DescriptionOfBusinessLineItems [Line Items] |  |  |  |  |  |  |  |  |  |
Self-sufficient installed capacity | MillionsTons |  |  |  |  | 4,700,000 |  |  |  |  |

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