XML 73 R57.htm IDEA: XBRL DOCUMENT v3.8.0.1
Mergers and Acquisitions - Pro-Forma Operating Results (Details) - Coffey and INDUS - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Oct. 01, 2017
Oct. 02, 2016
Pro forma operating results    
Revenue $ 2,753,360 $ 2,714,658
Operating income 183,342 152,676
Net income attributable to Tetra Tech $ 117,874 $ 98,871
Earnings per share attributable to Tetra Tech    
Basic (in dollars per share) $ 2.07 $ 1.7
Diluted (in dollars per share) $ 2.04 $ 1.68