Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 30, 2012
Consolidated Statements of Operations
Revenue	$ 2,483,814	$ 2,613,755	$ 2,711,075
Subcontractor costs	(623,896)	(588,923)	(689,005)
Other costs of revenue	(1,577,481)	(1,757,842)	(1,663,065)
Selling, general and administrative expenses	(187,298)	(199,732)	(210,970)
Contingent consideration - fair value adjustments	58,694	9,560	19,246
Impairment of goodwill		(56,600)	(914)
Operating income	153,833	20,218	166,367
Interest income	804	1,003	873
Interest expense	(10,294)	(8,689)	(6,444)
Income before income tax expense	144,343	12,532	160,796
Income tax expense	(35,668)	(14,038)	(56,064)
Net income (loss) including noncontrolling interests	108,675	(1,506)	104,732
Net income attributable to noncontrolling interests	(409)	(635)	(352)
Net income (loss) attributable to Tetra Tech	$ 108,266	$ (2,141)	$ 104,380
Net income (loss) attributable to Tetra Tech per share:
Basic (in dollars per share)	$ 1.68	$ (0.03)	$ 1.65
Diluted (in dollars per share)	$ 1.66	$ (0.03)	$ 1.63
Weighted-average common shares outstanding:
Basic (in shares)	64,379	64,544	63,217
Diluted (in shares)	65,146	64,544	63,934
Cash dividends paid per share	$ 0.14