Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jul. 02, 2017	Jun. 26, 2016	Jul. 02, 2017	Jun. 26, 2016
Condensed Consolidated Statements of Income
Revenue	$ 685,539	$ 666,869	$ 2,018,171	$ 1,854,961
Subcontractor costs	(187,061)	(168,235)	(518,188)	(456,606)
Other costs of revenue	(408,228)	(413,551)	(1,247,369)	(1,165,323)
Gross profit	90,250	85,083	252,614	233,032
Selling, general and administrative expenses	(44,366)	(44,993)	(131,068)	(124,626)
Acquisition and integration expenses		(1,005)		(16,916)
Contingent consideration - fair value adjustments			7,149	(2,823)
Operating income	45,884	39,085	128,695	88,667
Interest expense, net	(2,795)	(2,590)	(8,802)	(8,501)
Income before income tax expense	43,089	36,495	119,893	80,166
Income tax expense	(13,114)	(10,805)	(36,462)	(27,497)
Net income including noncontrolling interests	29,975	25,690	83,431	52,669
Net loss (income) from noncontrolling interests	8	4	(24)	9
Net income attributable to Tetra Tech	$ 29,983	$ 25,694	$ 83,407	$ 52,678
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.52	$ 0.44	$ 1.46	$ 0.90
Diluted (in dollars per share)	$ 0.52	$ 0.44	$ 1.44	$ 0.89
Weighted-average common shares outstanding:
Basic (in shares)	57,184	57,796	57,108	58,483
Diluted (in shares)	58,161	58,616	58,116	59,228
Cash dividends paid per share	$ 0.10	$ 0.09	$ 0.28	$ 0.25