Summary of significant accounting policies, Leased assets (Details) - Buildings and Facilities [Member]	12 Months Ended
Dec. 31, 2024
Minimum [Member]
Leased assets [Abstract]
Term of lease	1 year
Maximum [Member]
Leased assets [Abstract]
Term of lease	10 years

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	gtmay_OperatingLeaseTermOfContractLessee
Namespace Prefix:	gtmay_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration