Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Apr. 01, 2012	Apr. 03, 2011	Apr. 01, 2012	Apr. 03, 2011	Oct. 02, 2011
Financial information concerning reportable segments
Revenue	$ 624,345	$ 612,566	$ 1,306,972	$ 1,223,690
Segment operating income	35,543	29,256	71,635	63,581
Total assets	1,576,084		1,576,084		1,593,988
Engineering and consulting services (ECS)
Financial information concerning reportable segments
Revenue	251,486	225,958	497,149	431,348
Segment operating income	18,022	17,771	37,514	36,072
Total assets	808,139		808,139		767,347
Technical support services (TSS)
Financial information concerning reportable segments
Revenue	224,001	200,642	452,832	423,947
Segment operating income	17,063	13,458	32,565	29,247
Total assets	542,378		542,378		505,198
Engineering and architecture services (EAS)
Financial information concerning reportable segments
Revenue	79,788	73,659	161,422	141,642
Segment operating income	5,413	5,163	9,817	9,907
Total assets	114,592		114,592		111,555
Remediation and construction management (RCM)
Financial information concerning reportable segments
Revenue	117,414	134,921	278,171	279,485
Segment operating income	3,999	1,801	9,889	4,912
Total assets	278,981		278,981		296,361
Reportable Segments
Financial information concerning reportable segments
Revenue	672,689	635,180	1,389,574	1,276,422
Segment operating income	44,497	38,193	89,785	80,138
Total assets	$ 1,744,090		$ 1,744,090		$ 1,680,461