Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 02, 2017	Mar. 27, 2016	Apr. 02, 2017	Mar. 27, 2016
Condensed Consolidated Statements of Income
Revenue	$ 663,781	$ 627,384	$ 1,332,632	$ 1,188,092
Subcontractor costs	(151,827)	(148,619)	(331,127)	(288,371)
Other costs of revenue	(430,952)	(403,976)	(839,141)	(751,772)
Gross profit	81,002	74,789	162,364	147,949
Selling, general and administrative expenses	(45,195)	(40,406)	(86,702)	(79,634)
Acquisition and integration expenses		(15,911)		(15,911)
Contingent consideration - fair value adjustments	7,149	(1,822)	7,149	(2,823)
Operating income	42,956	16,650	82,811	49,581
Interest expense, net	(3,099)	(4,251)	(6,007)	(5,911)
Income before income tax expense	39,857	12,399	76,804	43,670
Income tax expense	(12,990)	(8,661)	(23,348)	(16,692)
Net income including noncontrolling interests	26,867	3,738	53,456	26,978
Net (income) loss from noncontrolling interests	(5)	6	(32)	5
Net income attributable to Tetra Tech	$ 26,862	$ 3,744	$ 53,424	$ 26,983
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.47	$ 0.06	$ 0.93	$ 0.46
Diluted (in dollars per share)	$ 0.46	$ 0.06	$ 0.92	$ 0.45
Weighted-average common shares outstanding:
Basic (in shares)	57,270	58,451	57,171	58,819
Diluted (in shares)	58,270	59,131	58,194	59,527
Cash dividends paid per share	$ 0.09	$ 0.08	$ 0.18	$ 0.16