Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Oct. 02, 2016	Sep. 27, 2015	Sep. 28, 2014
Consolidated Statements of Income
Revenue	$ 2,583,469	$ 2,299,321	$ 2,483,814
Subcontractor costs	(654,264)	(580,606)	(623,896)
Other costs of revenue	(1,598,994)	(1,402,925)	(1,577,481)
Gross profit	330,211	315,790	282,437
Selling, general and administrative expenses	(171,985)	(170,456)	(187,298)
Acquisition and integration expenses	(19,548)
Contingent consideration - fair value adjustments	(2,823)	3,113	58,694
Impairment of goodwill and other intangible assets		(60,763)
Operating income	135,855	87,684	153,833
Interest income	996	680	804
Interest expense	(12,385)	(8,043)	(10,294)
Income before income tax expense	124,466	80,321	144,343
Income tax expense	(40,613)	(41,093)	(35,668)
Net income including noncontrolling interests	83,853	39,228	108,675
Net income from noncontrolling interests	(70)	(154)	(409)
Net income attributable to Tetra Tech	$ 83,783	$ 39,074	$ 108,266
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 1.44	$ 0.64	$ 1.68
Diluted (in dollars per share)	$ 1.42	$ 0.64	$ 1.66
Weighted-average common shares outstanding:
Basic (in shares)	58,186	60,913	64,379
Diluted (in shares)	58,966	61,532	65,146
Cash dividends paid per share	$ 0.34	$ 0.30	$ 0.14