Subsequent events to the reporting date (Details) $ in Thousands	Dec. 02, 2020 MXN ($)
Subsequent events to the reporting date [Abstract]
Amount of advance received on sale of vessel	$ 63,700

The amount received in advance for the sale of an asset.

No definition available.

Name:	gtmay_AdvanceReceivedSaleOfAsset
Namespace Prefix:	gtmay_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant