XML 205 R198.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Financial Instruments and Risk Management - Summary of Changes in Value of Options (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of financial liabilities [line items] |  |  |
Variation in fair value | R$ 187 |  |
Put option - SAAG [member] |  |  |
Disclosure of financial liabilities [line items] |  |  |
Balance | 196 | R$ 148 | R$ 29
Variation in fair value | 121 |  |
Adjustment to fair value |  | 48 | 119
Reversals | (5) |  |
Balance | R$ 312 | R$ 196 | R$ 148

X
- Definition The amount of financial liabilities classified as derivative instruments. [Refer: Financial assets; Derivatives [member]] + 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
Name: | ifrs-full_DerivativeFinancialLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- 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
Name: | ifrs-full_DisclosureOfFinancialLiabilitiesLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The increase (decrease) in the fair value measurement of liabilities. [Refer: At fair value [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 13 -IssueDate 2017-01-01 -Paragraph 93 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2017-03-01&anchor=para_93_e&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_IncreaseDecreaseInFairValueMeasurementLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Adjustment to fair value of options. + References No definition available. + Details
Name: | xcmig_AdjustmentToFairValueOfOptions
Namespace Prefix: | xcmig_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reversals derivative financial liabilities. + References No definition available. + Details
Name: | xcmig_ReversalsDerivativeFinancialLiabilities
Namespace Prefix: | xcmig_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=xcmig_PutOptionSAAGMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |