Goodwill and Intangibles (Details) (USD $)	3 Months Ended	12 Months Ended						3 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Oct. 02, 2011	Sep. 30, 2012 Engineering and consulting services (ECS)	Oct. 02, 2011 Engineering and consulting services (ECS)	Sep. 30, 2012 Technical support services (TSS)	Oct. 02, 2011 Technical support services (TSS)	Sep. 30, 2012 Engineering and architecture services (EAS)	Sep. 30, 2012 Engineering and architecture services (EAS)	Oct. 02, 2011 Engineering and architecture services (EAS)	Sep. 30, 2012 Remediation and construction management (RCM)	Oct. 03, 2010 Remediation and construction management (RCM)
Goodwill
Balance at beginning of the period		$ 569,414,000	$ 394,422,000	$ 405,678,000	$ 244,616,000	$ 82,091,000	$ 68,661,000		$ 17,710,000	$ 17,210,000	$ 63,935,000	$ 63,935,000
Transfer out of segment				(29,338,000)							(16,097,000)
Transfer into segment						45,435,000
Goodwill additions		38,391,000	160,662,000	5,245,000	149,193,000	31,201,000	11,469,000				1,945,000
Currency translation adjustments		18,910,000	(3,486,000)	18,910,000	(3,486,000)
Goodwill adjustments		10,157,000	17,816,000	10,122,000	15,355,000	35,000	1,961,000			500,000
Goodwill impairment	(914,000)	(914,000)						(914,000)	(914,000)
Accumulated impairment losses								105,900,000	105,900,000	105,000,000
Balance at end of the period	635,958,000	635,958,000	569,414,000	410,617,000	405,678,000	158,762,000	82,091,000	16,796,000	16,796,000	17,710,000	49,783,000	63,935,000
Gross amount of goodwill								$ 122,700,000	$ 122,700,000	$ 122,700,000