Revenue (Disaggregation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 203,181	$ 194,162
Americas
Disaggregation of Revenue [Line Items]
Revenue	76,889
Europe
Disaggregation of Revenue [Line Items]
Revenue	53,975
Asia
Disaggregation of Revenue [Line Items]
Revenue	72,317
Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	157,240
Over time
Disaggregation of Revenue [Line Items]
Revenue	45,941
Product
Disaggregation of Revenue [Line Items]
Revenue	175,078	169,241
Service
Disaggregation of Revenue [Line Items]
Revenue	28,103	24,921
Test & Simulation
Disaggregation of Revenue [Line Items]
Revenue	125,560	118,203
Test & Simulation | Americas
Disaggregation of Revenue [Line Items]
Revenue	39,489
Test & Simulation | Europe
Disaggregation of Revenue [Line Items]
Revenue	28,627
Test & Simulation | Asia
Disaggregation of Revenue [Line Items]
Revenue	57,444
Test & Simulation | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	79,619
Test & Simulation | Over time
Disaggregation of Revenue [Line Items]
Revenue	45,941
Test & Simulation | Product
Disaggregation of Revenue [Line Items]
Revenue	98,907
Test & Simulation | Service
Disaggregation of Revenue [Line Items]
Revenue	26,653
Sensors
Disaggregation of Revenue [Line Items]
Revenue	77,950	75,959
Sensors | Americas
Disaggregation of Revenue [Line Items]
Revenue	37,729
Sensors | Europe
Disaggregation of Revenue [Line Items]
Revenue	25,348
Sensors | Asia
Disaggregation of Revenue [Line Items]
Revenue	14,873
Sensors | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	77,950
Sensors | Over time
Disaggregation of Revenue [Line Items]
Revenue	0
Sensors | Product
Disaggregation of Revenue [Line Items]
Revenue	76,500
Sensors | Service
Disaggregation of Revenue [Line Items]
Revenue	1,450
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue	(329)	$ 0
Intersegment Eliminations | Americas
Disaggregation of Revenue [Line Items]
Revenue	(329)
Intersegment Eliminations | Europe
Disaggregation of Revenue [Line Items]
Revenue	0
Intersegment Eliminations | Asia
Disaggregation of Revenue [Line Items]
Revenue	0
Intersegment Eliminations | Point-in-time
Disaggregation of Revenue [Line Items]
Revenue	(329)
Intersegment Eliminations | Over time
Disaggregation of Revenue [Line Items]
Revenue	0
Intersegment Eliminations | Product
Disaggregation of Revenue [Line Items]
Revenue	(329)
Intersegment Eliminations | Service
Disaggregation of Revenue [Line Items]
Revenue	$ 0