Name:	gtmay_FinancialLeasesAsLesseeAbstract
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The amount representing the difference between the future minimum finance lease payments and their present value. Minimum lease payments are payments over the lease term that the lessee is or can be required to make, excluding contingent rent, costs for services and taxes to be paid by, and reimbursed to, the lessor, together with: (a) for a lessee, any amounts guaranteed by the lessee or by a party related to the lessee; or (b) for a lessor, any residual value guaranteed to the lessor by: (i) the lessee; (ii) a party related to the lessee; or (iii) a third party unrelated to the lessor that is financially capable of discharging the obligations under the guarantee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2017-01-01
-Paragraph 31
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2017-03-02&anchor=para_31_b&doctype=Standard&book=B
-URIDate 2017-03-09

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Namespace Prefix:	ifrs-full_
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The amount of payments over the finance lease term that the lessee is or can be required to make, excluding contingent rent, costs for services and taxes to be paid by, and reimbursed to, the lessor, together with any amounts guaranteed by the lessee or by a party related to the lessee.

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

The present value of minimum finance lease payments payable. [Refer: Minimum finance lease payments payable]

Name:	ifrs-full_MinimumFinanceLeasePaymentsPayableAtPresentValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

The amount of assets recognised by the entity, which are leased under finance leases.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2017-01-01
-Paragraph 31
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2017-03-02&anchor=para_31_a&doctype=Standard&book=B
-URIDate 2017-03-09

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