Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Condensed Consolidated Statements of Income
Revenue	$ 575,108	$ 629,502	$ 1,720,927	$ 1,861,635
Subcontractor costs	(153,209)	(170,746)	(429,194)	(463,904)
Other costs of revenue	(340,181)	(381,319)	(1,061,419)	(1,164,761)
Selling, general and administrative expenses	(40,997)	(47,175)	(125,695)	(138,778)
Contingent consideration - fair value adjustments		8,905	3,113	34,878
Operating income	40,721	39,167	107,732	129,070
Interest expense	(2,026)	(2,454)	(5,621)	(7,373)
Income before income tax expense	38,695	36,713	102,111	121,697
Income tax expense	(12,443)	(10,002)	(31,202)	(35,751)
Net income including noncontrolling interests	26,252	26,711	70,909	85,946
Net income attributable to noncontrolling interests	(46)	(54)	(111)	(266)
Net income attributable to Tetra Tech	$ 26,206	$ 26,657	$ 70,798	$ 85,680
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.44	$ 0.41	$ 1.16	$ 1.32
Diluted (in dollars per share)	$ 0.43	$ 0.41	$ 1.14	$ 1.31
Weighted-average common shares outstanding:
Basic (in shares)	60,207	64,566	61,293	64,683
Diluted (in shares)	60,792	65,302	61,887	65,493
Cash dividends paid per share	$ 0.08	$ 0.07	$ 0.22	$ 0.07