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17. PROVISION FOR ENVIRONMENTAL LIABILITIES AND ASSET RETIREMENT OBLIGATIONS (Details) - BRL (R$) R$ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Disclosure of fair value measurement of liabilities [line items]
Provision for environmental liabilities and decommissioning of assets	R$ 337,013	R$ 347,064
Environmental liabilities
Disclosure of fair value measurement of liabilities [line items]
Provision for environmental liabilities and decommissioning of assets	255,517	273,475
Asset retirement obligations
Disclosure of fair value measurement of liabilities [line items]
Provision for environmental liabilities and decommissioning of assets	R$ 81,496	R$ 73,589

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- 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.

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- Definition

The amount of non-current provisions other than provisions for employee benefits. [Refer: Non-current provisions]

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_d&doctype=Standard
-URIDate 2017-03-09

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