XML 51 R49.htm IDEA: XBRL DOCUMENT
v3.19.3

Description of Business (Details) - segment | 12 Months Ended
--- | ---
Sep. 29, 2019 | Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |
Number of renamed reportable segments | 2 | 2

X
- Definition Number Of Renamed Reportable Segments + References No definition available. + Details
Name: | ttek_NumberOfRenamedReportableSegments
Namespace Prefix: | ttek_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration