Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 30, 2018	Dec. 31, 2017
Revenue	$ 717,431	$ 759,749
Gross profit	98,684	94,145
Selling, general and administrative expenses	(42,973)	(45,556)
Income from operations	55,711	48,589
Interest expense	(2,897)	(3,160)
Income before income tax (expense) benefit	52,814	45,429
Income tax (expense) benefit	(10,782)	623
Net income	42,032	46,052
Net income attributable to noncontrolling interests	(35)	(18)
Net income attributable to Tetra Tech	$ 41,997	$ 46,034
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.76	$ 0.82
Diluted (in dollars per share)	$ 0.75	$ 0.81
Weighted-average common shares outstanding:
Basic (in shares)	55,390	55,855
Diluted (in shares)	56,366	56,875
Cash dividends paid per share (in dollars per share)	$ 0.12	$ 0.1
Subcontractor
Cost of revenue	$ (164,067)	$ (214,902)
Other
Cost of revenue	$ (454,680)	$ (450,702)