Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Dec. 29, 2013	Dec. 30, 2012
Condensed Consolidated Statements of Income
Revenue	$ 645,848	$ 658,545
Subcontractor costs	(162,857)	(161,347)
Other costs of revenue	(396,528)	(408,995)
Selling, general and administrative expenses	(47,375)	(46,384)
Contingent consideration - fair value adjustments	4,630	(10)
Operating income	43,718	41,809
Interest expense	(2,424)	(1,185)
Income before income tax expense	41,294	40,624
Income tax expense	(13,967)	(14,228)
Net income including noncontrolling interests	27,327	26,396
Net income attributable to noncontrolling interests	(12)	(172)
Net income attributable to Tetra Tech	$ 27,315	$ 26,224
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.43	$ 0.41
Diluted (in dollars per share)	$ 0.42	$ 0.41
Weighted-average common shares outstanding:
Basic (in shares)	64,227	63,864
Diluted (in shares)	65,048	64,608