Basis of Presentation and Preparation - Narrative (Details) $ in Millions	Oct. 02, 2022 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Government assistance, amount, cumulative, current	$ 26.0
Government assistance, amount expected to be recognized in next twelve months	9.0
Government assistance, amount, cumulative, noncurrent	$ 17.0

Government Assistance, Amount Expected To Be Recognized In Next Twelve Months

No definition available.

Name:	ttek_GovernmentAssistanceAmountExpectedToBeRecognizedInNextTwelveMonths
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant