XML 60 R45.htm IDEA: XBRL DOCUMENT
v3.10.0.1

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