Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2012	Jul. 02, 2011	Jun. 30, 2012	Jul. 02, 2011
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Number of reportable segments	2	2	2	2
Number of operating segments	3	3	3	3
Revenue	$ 141,697	$ 116,832	$ 404,413	$ 335,769
Income from operations	18,182	15,624	58,930	51,967
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	116,338	89,346	327,879	258,649
Income from operations	13,674	8,941	42,141	31,536
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	25,359	27,486	76,534	77,120
Income from operations	$ 4,508	$ 6,683	$ 16,789	$ 20,431