Reportable Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jan. 01, 2012	Jan. 02, 2011	Oct. 02, 2011
Financial information concerning reportable segments
Revenue	$ 682,627	$ 611,124
Segment operating income	36,093	34,325
Total assets	1,600,627		1,593,988
Engineering and consulting services (ECS)
Financial information concerning reportable segments
Revenue	245,663	205,389
Segment operating income	19,491	18,301
Total assets	792,491		767,347
Technical support services (TSS)
Financial information concerning reportable segments
Revenue	228,832	223,305
Segment operating income	15,502	15,789
Total assets	505,309		505,198
Engineering and architecture services (EAS)
Financial information concerning reportable segments
Revenue	81,633	67,983
Segment operating income	4,405	4,744
Total assets	110,112		111,555
Remediation and construction management (RCM)
Financial information concerning reportable segments
Revenue	160,758	144,565
Segment operating income	5,890	3,111
Total assets	303,667		296,361
Reportable Segments
Financial information concerning reportable segments
Revenue	716,886	641,242
Segment operating income	45,288	41,945
Total assets	$ 1,711,579		$ 1,680,461