Summary of significant accounting policies, Climate-related issues (Details)	12 Months Ended
Dec. 31, 2024
Climate-related issues [Abstract]
Minimum period to achieve self-sufficiency	25 years

Minimum period that the company expects to achieve self-sufficiency in its operations through its commitment to energy efficiency.

No definition available.

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