Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jul. 01, 2012	Jul. 03, 2011	Jul. 01, 2012	Jul. 03, 2011	Oct. 02, 2011
Financial information concerning reportable segments
Revenue	$ 684,698	$ 673,792	$ 1,991,670	$ 1,897,482
Operating income	46,261	39,408	117,896	102,989
Total assets	1,709,619		1,709,619		1,593,988
Engineering and consulting services (ECS)
Financial information concerning reportable segments
Revenue	263,666	242,958	760,815	674,306
Operating income	24,484	23,456	61,998	59,528
Total assets	861,846		861,846		767,347
Technical support services (TSS)
Financial information concerning reportable segments
Revenue	234,390	216,452	687,222	640,399
Operating income	17,810	14,361	50,375	43,608
Total assets	573,423		573,423		505,198
Engineering and architecture services (EAS)
Financial information concerning reportable segments
Revenue	82,078	77,983	243,500	219,625
Operating income	5,488	6,491	15,305	16,399
Total assets	120,445		120,445		111,555
Remediation and construction management (RCM)
Financial information concerning reportable segments
Revenue	153,860	170,137	432,032	449,622
Operating income	6,184	2,803	16,073	7,714
Total assets	322,687		322,687		296,361
Elimination of inter-segment revenue
Financial information concerning reportable segments
Revenue	(49,296)	(33,738)	(131,899)	(86,470)
Corporate
Financial information concerning reportable segments
Operating income	(7,705)	(7,703)	(25,855)	(24,260)
Assets not allocated to segments and intercompany eliminations
Financial information concerning reportable segments
Total assets	$ (168,782)		$ (168,782)		$ (86,473)