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Post-Retirement Obligation - Summary of Changes in Net Liabilities (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of defined benefit plans [line items] |  |  |
Current liabilities | R$ 232 | R$ 199 |
Non-currentliabilities | 3,954 | 4,043 |
Net liabilities, Beginning balance | 4,242 | 3,253 | R$ 2,631
Expense recognized in Statement of income | 455 | 448 | 359
Contributions paid | (282) | (240) | (208)
Plan amendment - Past service | (619) |  | (74)
Actuarial losses (gains) | 390 | 781 | 545
Net liabilities, Ending balance | 4,186 | 4,242 | 3,253
Pension plans and retirement supplement plans [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Net liabilities, Beginning balance | 1,679 | 1,346 | 798
Expense recognized in Statement of income | 175 | 187 | 129
Contributions paid | (160) | (128) | (116)
Actuarial losses (gains) | 374 | 274 | 535
Net liabilities, Ending balance | 2,068 | 1,679 | 1,346
Health plan [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Net liabilities, Beginning balance | 1,711 | 1,323 | 1,120
Expense recognized in Statement of income | 189 | 182 | 142
Contributions paid | (113) | (99) | (77)
Actuarial losses (gains) | 22 | 305 | 138
Net liabilities, Ending balance | 1,809 | 1,711 | 1,323
Dental plan [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Net liabilities, Beginning balance | 38 | 30 | 33
Expense recognized in Statement of income | 3 | 4 | 4
Contributions paid | (2) | (2) | (3)
Actuarial losses (gains) | (1) | 6 | (4)
Net liabilities, Ending balance | 38 | 38 | 30
Life insurance [member] |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Net liabilities, Beginning balance | 814 | 554 | 680
Expense recognized in Statement of income | 88 | 75 | 84
Contributions paid | (7) | (11) | (12)
Plan amendment - Past service | (619) |  | (74)
Actuarial losses (gains) | (5) | 196 | (124)
Net liabilities, Ending balance | R$ 271 | R$ 814 | R$ 554

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- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph c -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_iii&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of current net defined benefit liability. [Refer: Net defined benefit liability] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_55&doctype=Standard -URIDate 2017-03-09 + Details
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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. + References No definition available. + Details
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- Definition The amount of employer contributions to 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 i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=26&date=2017-03-01&anchor=para_35_b_i&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The amount of non-current net defined benefit liability. [Refer: Net defined benefit liability] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_55&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from past service cost and gains (losses) arising from settlements. [Refer: Gains (losses) arising from settlements, net defined benefit liability (asset); Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_d&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The present value of the defined benefit obligation, less the fair value of the plan assets (if any). [Refer: Plan assets [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_57_a&doctype=Standard -URIDate 2017-03-09 + Details
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