Revenue (Disaggregation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 828,586	$ 892,518	$ 778,032
Americas
Disaggregation of Revenue [Line Items]
Revenue	323,626	346,538
Europe
Disaggregation of Revenue [Line Items]
Revenue	236,428	224,982	223,236
Asia
Disaggregation of Revenue [Line Items]
Revenue	268,532	320,998
Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	533,887	668,896
Over time
Disaggregation of Revenue [Line Items]
Revenue	294,699	223,622
Product
Disaggregation of Revenue [Line Items]
Revenue	726,028	782,012	674,391
Service
Disaggregation of Revenue [Line Items]
Revenue	102,558	110,506	103,641
Test & Simulation
Disaggregation of Revenue [Line Items]
Revenue	490,634	558,908	464,924
Sensors
Disaggregation of Revenue [Line Items]
Revenue	339,223	334,976	314,269
Operating Segments | Test & Simulation
Disaggregation of Revenue [Line Items]
Revenue	490,634	558,908
Operating Segments | Test & Simulation | Americas
Disaggregation of Revenue [Line Items]
Revenue	144,565	179,421
Operating Segments | Test & Simulation | Europe
Disaggregation of Revenue [Line Items]
Revenue	145,758	120,164
Operating Segments | Test & Simulation | Asia
Disaggregation of Revenue [Line Items]
Revenue	200,311	259,323
Operating Segments | Test & Simulation | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	231,738	356,907
Operating Segments | Test & Simulation | Over time
Disaggregation of Revenue [Line Items]
Revenue	258,896	202,001
Operating Segments | Test & Simulation | Product
Disaggregation of Revenue [Line Items]
Revenue	398,324	455,715
Operating Segments | Test & Simulation | Service
Disaggregation of Revenue [Line Items]
Revenue	92,310	103,193
Operating Segments | Sensors
Disaggregation of Revenue [Line Items]
Revenue	339,223	334,976
Operating Segments | Sensors | Americas
Disaggregation of Revenue [Line Items]
Revenue	180,332	168,483
Operating Segments | Sensors | Europe
Disaggregation of Revenue [Line Items]
Revenue	90,670	104,818
Operating Segments | Sensors | Asia
Disaggregation of Revenue [Line Items]
Revenue	68,221	61,675
Operating Segments | Sensors | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	303,420	313,355
Operating Segments | Sensors | Over time
Disaggregation of Revenue [Line Items]
Revenue	35,803	21,621
Operating Segments | Sensors | Product
Disaggregation of Revenue [Line Items]
Revenue	328,944	327,663
Operating Segments | Sensors | Service
Disaggregation of Revenue [Line Items]
Revenue	10,279	7,313
Intersegment
Disaggregation of Revenue [Line Items]
Revenue	(1,271)	(1,366)	$ (1,161)
Intersegment | Americas
Disaggregation of Revenue [Line Items]
Revenue	(1,271)	(1,366)
Intersegment | Europe
Disaggregation of Revenue [Line Items]
Revenue	0	0
Intersegment | Asia
Disaggregation of Revenue [Line Items]
Revenue	0	0
Intersegment | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	(1,271)	(1,366)
Intersegment | Over time
Disaggregation of Revenue [Line Items]
Revenue	0	0
Intersegment | Product
Disaggregation of Revenue [Line Items]
Revenue	(1,240)	(1,366)
Intersegment | Service
Disaggregation of Revenue [Line Items]
Revenue	$ (31)	$ 0