Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Jan. 01, 2011	Oct. 01, 2011
Business Segment Information [Abstract]
Number of operating segments	3	3	3
Number of reportable segments	2	2	2
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	$ 133,697	$ 105,876
Income from operations	23,549	18,474
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	108,628	82,542
Income from operations	17,773	12,753
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	25,069	23,334
Income from operations	$ 5,776	$ 5,721