Reportable Segments (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Jul. 03, 2011	Jun. 27, 2010	Jul. 03, 2011	Jun. 27, 2010	Oct. 03, 2010
Financial information concerning reportable segments
Revenue	$ 673,792	$ 562,365	$ 1,897,482	$ 1,573,850
Segment operating income	39,408	32,706	102,989	87,349
Depreciation expense	7,009	5,203	20,401	14,958
Total assets	1,571,827		1,571,827		1,381,689
Reportable Segments.
Financial information concerning reportable segments
Revenue	707,530	594,886	1,983,952	1,647,140
Segment operating income	47,111	37,475	127,249	100,784
Depreciation expense	6,261	4,444	18,150	12,859
Total assets	1,699,478		1,699,478		1,320,490
Engineering and consulting services (ECS)
Financial information concerning reportable segments
Revenue	288,103	184,635	804,328	508,997
Segment operating income	26,227	13,738	67,569	38,671
Depreciation expense	2,991	1,296	8,470	4,089
Total assets	922,151		922,151		618,025
Technical support services (TSS)
Financial information concerning reportable segments
Revenue	141,436	131,139	425,435	381,533
Segment operating income	10,131	9,520	30,748	29,906
Depreciation expense	256	159	797	471
Total assets	323,085		323,085		281,376
Engineering and architecture services (EAS)
Financial information concerning reportable segments
Revenue	77,983	76,688	219,625	211,404
Segment operating income	6,491	4,337	16,398	7,454
Depreciation expense	452	506	1,405	1,608
Total assets	117,142		117,142		93,696
Remediation and construction management (RCM)
Financial information concerning reportable segments
Revenue	200,008	202,424	534,564	545,206
Segment operating income	4,262	9,880	12,534	24,753
Depreciation expense	2,562	2,483	7,478	6,691
Total assets	$ 337,100		$ 337,100		$ 327,393