Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2016	Mar. 29, 2015	Mar. 27, 2016	Mar. 29, 2015
Condensed Consolidated Statements of Comprehensive Income (Loss)
Net income including noncontrolling interests	$ 3,738	$ 19,010	$ 26,978	$ 44,656
Other comprehensive income, net of tax
Foreign currency translation adjustments	26,579	(43,680)	10,105	(68,189)
(Loss) gain on cash flow hedge valuations	(597)	(1,517)	513	(1,997)
Other comprehensive income (loss), net of tax	25,982	(45,197)	10,618	(70,186)
Comprehensive income (loss) including noncontrolling interests	29,720	(26,187)	37,596	(25,530)
Net loss (income) attributable to noncontrolling interests	6	7	5	(64)
Foreign currency translation adjustments, net of tax	(4)	164	(13)	104
Comprehensive income (loss) attributable to noncontrolling interests	2	171	(8)	40
Comprehensive income (loss) attributable to Tetra Tech	$ 29,722	$ (26,016)	$ 37,588	$ (25,490)