Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Oct. 02, 2011	Oct. 03, 2010
Revenue	$ 2,711,075	$ 2,573,144	$ 2,201,232
Subcontractor costs	(689,005)	(780,817)	(741,002)
Other costs of revenue	(1,663,065)	(1,454,374)	(1,172,542)
Selling, general and administrative expenses	(211,884)	(193,286)	(163,479)
Contingent consideration - fair value adjustments	19,246	1,755	265
Operating income	166,367	146,422	124,474
Interest income	873	879	801
Interest expense	(6,444)	(6,809)	(2,188)
Income before income tax expense	160,796	140,492	123,087
Income tax expense	(56,064)	(47,510)	(46,268)
Net income including noncontrolling interests	104,732	92,982	76,819
Net income attributable to noncontrolling interests	(352)	(2,943)
Net income attributable to Tetra Tech	$ 104,380	$ 90,039	$ 76,819
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 1.65	$ 1.45	$ 1.25
Diluted (in dollars per share)	$ 1.63	$ 1.43	$ 1.24
Weighted-average common shares outstanding:
Basic (in shares)	63,217	62,053	61,430
Diluted (in shares)	63,934	62,775	62,087