Commitments and contingencies, Commitments (Details) - MXN ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Commitments [Abstract]
Concession fees	$ 18,924	$ 17,589

The total fixed and variable periodic payments pursuant to maintaining concessional rights.

No definition available.

Name:	gtmay_ConcessionFeesExpense
Namespace Prefix:	gtmay_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration