Business Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 29, 2012 segment	Dec. 31, 2011
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Number of operating segments	2
Revenue	$ 142,668	$ 133,697
Income from operations	20,057	23,549
Test [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	121,103	108,628
Income from operations	16,391	17,773
Sensors [Member]
Segment Reporting, Reconciliation of Financial Information from Segments to Consolidated[Line Items]
Revenue	21,565	25,069
Income from operations	$ 3,666	$ 5,776