Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Sep. 30, 2012	Oct. 02, 2011	Oct. 03, 2010
Comprehensive Income
Net income including noncontrolling interests	$ 104,732	$ 92,982	$ 76,819
Other comprehensive income:
Foreign currency translation adjustment	26,486	(13,955)	6,874
Foreign currency hedge	(194)	438	(337)
Comprehensive income including noncontrolling interests	131,024	79,465	83,356
Net income attributable to noncontrolling interests	(352)	(2,943)
Foreign currency translation adjustment	(29)	(492)
Comprehensive income attributable to noncontrolling interests	(381)	(3,435)
Comprehensive income attributable to Tetra Tech	$ 130,643	$ 76,030	$ 83,356

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

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