Basis of Presentation and Preparation - Narrative (Details) $ in Millions	Oct. 01, 2023 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Government assistance, amount, cumulative, current	$ 21.0
Government Assistance, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities
Government assistance, amount expected to be recognized in next twelve months	$ 10.0
Government assistance, amount, cumulative, noncurrent	$ 11.0
Government Assistance, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other non-current liabilities

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

- Definition

Amount of cumulative government assistance recognized classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 832
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483507/832-10-50-3

+ Details

Name:	us-gaap_GovernmentAssistanceAmountCumulativeCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cumulative government assistance recognized classified as noncurrent.

+ References

+ Details

Name:	us-gaap_GovernmentAssistanceAmountCumulativeNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes government assistance classified as current.

+ References

+ Details

Name:	us-gaap_GovernmentAssistanceCurrentStatementOfFinancialPositionExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes government assistance classified as noncurrent.

+ References

+ Details

Name:	us-gaap_GovernmentAssistanceNoncurrentStatementOfFinancialPositionExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration