Represents the unbilled accounts receivable related to claims and requests for equitable adjustment on contracts.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the amount of remaining estimated costs to complete the contracts.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Revenue, Remaining Performance Obligation, Termination Notice Period One

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Revenue, Remaining Performance Obligation, Termination Notice Period Three

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Revenue, Remaining Performance Obligation, Termination Notice Period Two

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
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- Definition

Represents the period within which substantially all unbilled receivables are expected to be billed and collected.

+ References

No definition available.

+ Details

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Namespace Prefix:	ttek_
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- Definition

Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which (increases) decreases obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130549-203045

+ Details

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cumulative provision for contract losses not offset against related costs accumulated on the balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 35
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123355788&loc=d3e57777-111642

+ Details

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

- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

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- Details

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Revenue and Contract Balances - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jul. 03, 2022	Jun. 27, 2021	Jul. 03, 2022	Jun. 27, 2021	Oct. 03, 2021
Disaggregation of Revenue [Line Items]
Contract liability revenue recognized during the period			$ 111,000,000	$ 108,000,000
Net favorable (unfavorable) revenue and operating income adjustments	$ (2,800,000)	$ 1,700,000	2,200,000	2,800,000
Liabilities for anticipated losses	11,100,000		11,100,000		$ 12,700,000
Estimated cost to complete the related contracts	84,000,000		$ 84,000,000		104,000,000
Period for billing and collecting unbilled receivables			12 months
Remaining unsatisfied performance obligation	3,495,454,000		$ 3,495,454,000
Remaining performance obligation, termination notice period one			30 days
Remaining performance obligation, termination notice period two			60 days
Remaining performance obligation, termination notice period three			90 days
RCM
Disaggregation of Revenue [Line Items]
Accounts receivable related to claims and requests for equitable adjustment on contracts	$ 0		$ 0		$ 11,000,000
CIG
Disaggregation of Revenue [Line Items]
Net favorable (unfavorable) revenue and operating income adjustments			$ 0	$ 2,800,000