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Post-Retirement Liabilities - Additional Information (Detail) - BRL (R$) R$ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Feb. 28, 2018 | May 31, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of defined benefit plans [line items] |  |  |  |  |
Obligation for past actuarial deficits relating to pension fund |  |  | R$ 721 | R$ 787 |
Obligation for past actuarial deficits amortization description |  |  | Being amortized by June 2024, through monthly installments calculated by the system of constant installments (known as the 'Price' table), and adjusted by the IPCA (Expanded National Customer Price) inflation index (published by the Brazilian Geography and Statistics Institute - IBGE) plus 6% per year. |  |
Obligation rate for actuarial assumption |  |  | 6.00% |  |
Costs of post-employment obligations |  |  | R$ 65 | 103 | R$ 129
Financial costs and monetary updating expence |  |  | 65 | 103 | 129
Life insurance, a recovery of expense |  |  | 619 |  | 74
Post Employment Benefit Obligations [Member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Costs of post-employment obligations |  |  | 391 | R$ 345 | R$ 230
Pension Funds [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Expected employer contributions |  |  | 166 |  |
Defined contribution plan [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Expected employer contributions |  |  | R$ 90 |  |
Entering into significant commitments or contingent liabilities [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Remuneratory interest | 6.00% |  |  |  |
deficit found in Plan | R$ 99 |  |  |  |
Monthly installments | 167 monthly installments |  |  |  |
Forluz pension [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Retirement benefits plan |  | R$ 283 |  |  |
Remuneratory interest |  | 6.00% |  |  |

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- Definition The present value of the expected payments by a retirement benefit plan to existing and past employees, attributable to the service already rendered. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 26 -IssueDate 2017-01-01 -Paragraph 35 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=26&date=2017-03-01&anchor=para_35_d&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of benefits paid or payable for retirement benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 26 -IssueDate 2017-01-01 -Paragraph 35 -Subparagraph b -Clause v -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=26&date=2017-03-01&anchor=para_35_b_v&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of post-employment benefit expense relating to defined contribution plans. Defined contribution plans are post-employment benefit plans under which an entity pays fixed contributions into a separate entity (a fund) and will have no legal or constructive obligation to pay further contributions if the fund does not hold sufficient assets to pay all employee benefits relating to employee service in the current and prior periods. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 53 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_53&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition Deficit (surplus) of defined benefit pension plan. + References No definition available. + Details
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