XML 201 R194.htm IDEA: XBRL DOCUMENT
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Related Party transactions - Summary of Total Costs of Key Management Personnel (Detail) - BRL (R$) R$ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of key management personnel compensation [abstract] |  |  |
Remuneration | R$ 32 | R$ 25 | R$ 19
Profit sharing (reversal) | 1 | (1) | 2
Assistance benefits | 2 | 2 | 1
Total | R$ 35 | R$ 26 | R$ 22

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- Definition The amount of compensation to key management personnel. [Refer: Key management personnel of entity or parent [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 24 -IssueDate 2017-01-01 -Paragraph 17 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2017-03-01&anchor=para_17&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_KeyManagementPersonnelCompensation
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Disclosure of key management personnel compensation. + References No definition available. + Details
Name: | xcmig_DisclosureOfKeyManagementPersonnelCompensationAbstract
Namespace Prefix: | xcmig_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Key management personnel assistance benefits. + References No definition available. + Details
Name: | xcmig_KeyManagementPersonnelAssistanceBenefits
Namespace Prefix: | xcmig_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Key management personnel compensation salaries and other benefits. + References No definition available. + Details
Name: | xcmig_KeyManagementPersonnelCompensationSalariesAndOtherBenefits
Namespace Prefix: | xcmig_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Key management personnel profit shares (reversals). + References No definition available. + Details
Name: | xcmig_KeyManagementPersonnelProfitSharesReversals
Namespace Prefix: | xcmig_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration