Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing the amount excluded from the assessment of hedge effectiveness.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of derivative agreements entered into by the entity during the reporting period.

+ References

No definition available.

+ Details

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Estimated period for the anticipated transfer of gain (loss), net, from accumulated other comprehensive income into earnings, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimateOfTimeToTransfer1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossRecognizedInOtherComprehensiveIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ttek_InterestRateSwapAgreementBearingFixedRate1.36PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ttek_InterestRateSwapAgreementBearingFixedRate1.34PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ttek_InterestRateSwapAgreementBearingFixedRate1.35PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ttek_InterestRateSwapAgreementBearingFixedRate1.23PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ttek_InterestRateSwapAgreementBearingFixedRate1.24PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivative Financial Instruments - General Information (Details) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 29, 2013 item	Apr. 02, 2017 USD ($)	Oct. 02, 2016 USD ($)	Sep. 29, 2013 item
Interest rate swap agreements \| Derivatives designated as hedging instruments
Derivative Financial Instruments
Amounts excluded from effectiveness testing		$ 0	$ 0
Interest rate swap agreements \| Designated as cash flow hedges \| Derivatives designated as hedging instruments
Derivative Financial Instruments
Number of derivative agreements \| item	2			3
Amount of effective portion of derivatives before tax effect		$ 100
Period of reclassification from accumulated other comprehensive income (loss) to interest expense		12 months
Interest rate swap agreement bearing fixed rate 1.36%
Derivative Financial Instruments
Notional Amount		$ 42,281
Fixed Rate (as a percent)		1.36%
Interest rate swap agreement bearing fixed rate 1.34%
Derivative Financial Instruments
Notional Amount		$ 42,281
Fixed Rate (as a percent)		1.34%
Interest rate swap agreement bearing fixed rate 1.35%
Derivative Financial Instruments
Notional Amount		$ 42,281
Fixed Rate (as a percent)		1.35%
Interest rate swap agreement bearing fixed rate 1.23%
Derivative Financial Instruments
Notional Amount		$ 21,141
Fixed Rate (as a percent)		1.23%
Interest rate swap agreement bearing fixed rate 1.24%
Derivative Financial Instruments
Notional Amount		$ 21,141
Fixed Rate (as a percent)		1.24%
Foreign exchange forward contract \| Derivatives designated as hedging instruments
Derivative Financial Instruments
Amounts excluded from effectiveness testing		$ 0	$ 0