Earnings Per Share (Tables)

12 Months Ended

Oct. 01, 2017

Earnings Per Share [Abstract]

Schedule of number of weighted-average shares used to compute basic and diluted EPS

The following table sets forth the number of weighted-average shares used to compute basic and diluted EPS:

	Fiscal Year Ended
	October 1, 2017		October 2, 2016		September 27, 2015
	(in thousands, except per share data)
Net income attributable to Tetra Tech	$	117,874	$	83,783	$	39,074
Weighted-average common shares outstanding – basic	56,911		58,186		60,913
Effect of diluted stock options and unvested restricted stock	1,002		780		619
Weighted-average common stock outstanding – diluted	57,913		58,966		61,532
Earnings per share attributable to Tetra Tech:
Basic	$	2.07	$	1.44	$	0.64
Diluted	$	2.04	$	1.42	$	0.64