Basis of Presentation (Details)	3 Months Ended
Dec. 28, 2014 segment
Basis of Presentation
Number of renamed reportable segments	2

Represents the number of renamed reportable segments.

No definition available.

Name:	ttek_NumberOfRenamedReportableSegments
Namespace Prefix:	ttek_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration