Name:	ttek_BusinessAcquisitionContingentConsiderationActualCashPaymentReportedAsCashFlowsFromOperatingActivities
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

Name:	ttek_EarnOutPaymentsAbstract
Namespace Prefix:	ttek_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	ttek_EstimatedContingentEarnOutLiabilityRollForward
Namespace Prefix:	ttek_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of estimated earn-out liabilities for acquisitions during the period.

No definition available.

Name:	ttek_EstimatedEarnOutLiabilitiesForAcquisitionsDuringThePeriod
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the change in earn-out liability during the period resulting from the process of translating earn-out liability from business combination into the reporting currency of the reporting entity.

No definition available.

Name:	ttek_ForeignCurrencyTransactionAndTranslationAdjustment
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the change in fair value of contingent consideration reported in interest expense.

No definition available.

Name:	ttek_IncreaseDecreaseInFairValueOfContingentConsiderationReportedInInterestExpense
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the change in fair value of contingent consideration reported in operating income.

No definition available.

Name:	ttek_IncreaseDecreaseInFairValueOfContingentConsiderationReportedInOperatingIncome
Namespace Prefix:	ttek_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of liability recognized arising from contingent consideration in a business combination.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of cash outflow, not made soon after acquisition date of business combination, to settle contingent consideration liability up to amount recognized at acquisition date, including, but not limited to, measurement period adjustment and less amount paid soon after acquisition date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585