Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income (Loss)
Net income (loss) including noncontrolling interests	$ 108,675	$ (1,506)	$ 104,732
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	(45,480)	(28,817)	26,486
Gain (loss) on cash flow hedge valuations	1,029	(389)	(194)
Other comprehensive income (loss), net of tax	(44,451)	(29,206)	26,292
Comprehensive income (loss) including noncontrolling interests	64,224	(30,712)	131,024
Net income attributable to noncontrolling interests	(409)	(635)	(352)
Foreign currency translation adjustments, net of tax	55	47	(29)
Comprehensive income attributable to noncontrolling interests	(354)	(588)	(381)
Comprehensive income (loss) attributable to Tetra Tech	$ 63,870	$ (31,300)	$ 130,643