Business Segment Information (Financial Information by Reportable Segment) (Details) $ in Thousands	3 Months Ended
	Dec. 28, 2019 USD ($) segment	Dec. 29, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	2
Total revenue	$ 205,843	$ 203,181
Total income from operations	15,158	17,966
Operating Segments | Test & Simulation
Segment Reporting Information [Line Items]
Total revenue	120,730	125,560
Total income from operations	6,996	7,331
Operating Segments | Sensors
Segment Reporting Information [Line Items]
Total revenue	85,535	77,950
Total income from operations	8,159	10,634
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenue	(422)	(329)
Total income from operations	$ 3	$ 1