Restructuring and Related Costs (Summary of Restructuring Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Mar. 31, 2018	Apr. 01, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 362	$ 381	$ 608	$ 944
Test
Restructuring Cost and Reserve [Line Items]
Restructuring charges	346	0	601	0
Sensors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	16	381	7	944
Cost of sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges	304	254	424	580
Cost of sales | Test
Restructuring Cost and Reserve [Line Items]
Restructuring charges	304	0	424	0
Cost of sales | Sensors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	254	0	580
Selling and marketing
Restructuring Cost and Reserve [Line Items]
Restructuring charges	16	45	7	126
Selling and marketing | Test
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	0	0	0
Selling and marketing | Sensors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	16	45	7	126
General and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring charges	42	82	177	238
General and administrative | Test
Restructuring Cost and Reserve [Line Items]
Restructuring charges	42	0	177	0
General and administrative | Sensors
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0	$ 82	$ 0	$ 238