Name:	ttek_BusinessCombinationContingentConsiderationPaymentPeriod
Namespace Prefix:	ttek_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents a number of financial institutions, in any such number of which the entity limits the amount of investment exposure in order to control credit risk.

No definition available.

Name:	ttek_ConcentrationOfCreditRiskNumberOfFinancialInstitutionsForInvestmentExposure
Namespace Prefix:	ttek_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Cumulative Effect Of New Accounting Principle In Period Of Adoption, Percentage Decrease

No definition available.

Name:	ttek_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoptionPercentageDecrease
Namespace Prefix:	ttek_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of accounts receivable due from various agencies of the U.S. federal government.

No definition available.

Name:	ttek_PercentageOfAccountReceivablesDueFromAgencies
Namespace Prefix:	ttek_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of revenue from customers within the risk category.

No definition available.

Name:	ttek_PercentageOfRevenueEarnedFromAgencies
Namespace Prefix:	ttek_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

Name:	us-gaap_IntangibleAssetsNetIncludingGoodwillAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

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

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MajorCustomersAxis=ttek_FederalGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_MajorCustomersAxis=ttek_CommercialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: