Represents the period within which the majority of billings in excess of costs on uncompleted contracts will be earned.

No definition available.

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

- Definition

Represents the length of fiscal year.

+ References

No definition available.

+ Details

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

- Definition

Represents the high end of the range of length of fiscal year.

+ References

No definition available.

+ Details

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

- Definition

Represents the low end of the range of length of fiscal year.

+ References

No definition available.

+ Details

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

- Definition

Represents the maximum original term to maturity of an instrument to classify it as a cash equivalent.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of types of contracts under which revenue is recognized for work performed.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of types of fixed-price contracts.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

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

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Paragraph 80

-Subparagraph Exhibit 4-8, 3

-IssueDate 2006-05-01

-Chapter 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_RestrictedCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

Basis of Presentation and Preparation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 29, 2013 item	Sep. 30, 2012	Oct. 02, 2011
Principles of Consolidation and Presentation
Number of weeks in a fiscal year, low end of range	364 days
Number of weeks in a fiscal year, high end of range	371 days
Number of weeks in a fiscal year	364 days	364 days	364 days
Revenue Recognition and Contract Costs
Number of types of contracts under which revenue is recognized	3
Number of types of fixed-price contracts	2
Cash and Cash Equivalents
Maximum term of original maturity to classify instrument as cash equivalent	90 days
Restricted cash included in "Prepaid expenses and other current assets"	$ 4.5	$ 5.0
Accounts Receivable - Net
Period for billing and collecting unbilled receivables	12 months
Period for earning majority of billings in excess of costs	12 months
Equipment \| Maximum
Estimated useful lives
Estimated useful lives	10 years
Equipment \| Minimum
Estimated useful lives
Estimated useful lives	3 years
Furniture and fixtures \| Maximum
Estimated useful lives
Estimated useful lives	10 years
Furniture and fixtures \| Minimum
Estimated useful lives
Estimated useful lives	3 years
Buildings \| Maximum
Estimated useful lives
Estimated useful lives	40 years