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

Represents the gain (loss) on the fair value adjustments for contingent earn-out liabilities.

No definition available.

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

Represents the earn out period for operating income projection used for fair value measurement.

No definition available.

Name:	ttek_BusinessAcquisitionEarnOutPeriodForOperatingIncomeProjectionsUsedInFairValueMeasurement
Namespace Prefix:	ttek_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

Represents the number of acquisitions completed.

No definition available.

Name:	ttek_NumberOfAcquisitionsCompleted
Namespace Prefix:	ttek_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Details

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

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 35

-Paragraph 1

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

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

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266