Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Apr. 02, 2011	Mar. 31, 2012	Apr. 02, 2011
Business Segment Information [Abstract]
Number of operating segments			3
Number of reportable segments			2
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	$ 129,019	$ 113,061	$ 262,716	$ 218,937
Income from operations	17,199	17,869	40,748	36,343
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	102,913	86,761	211,541	169,303
Income from operations	10,694	9,842	28,467	22,595
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	26,106	26,300	51,175	49,634
Income from operations	$ 6,505	$ 8,027	$ 12,281	$ 13,748