Business Segment Information (Financial Information By Reportable Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Oct. 01, 2016
Segment Reporting Information [Line Items]
Revenue	$ 778,032	$ 787,955	$ 650,147
Income from Operations	65,172	54,828	41,763
Identifiable Assets	1,139,396	1,189,692	1,188,020
Goodwill	369,275	369,762	369,700
Capital Expenditures	12,321	17,798	20,806
Depreciation and Amortization	34,492	35,523	24,077
Test [Member]
Segment Reporting Information [Line Items]
Revenue	464,924	504,087	512,265
Income from Operations	19,225	28,622	40,660
Identifiable Assets	299,242	374,698	395,067
Goodwill	24,631	25,109	25,022
Capital Expenditures	8,111	13,281	17,570
Depreciation and Amortization	16,353	17,275	17,279
Sensors [Member]
Segment Reporting Information [Line Items]
Revenue	314,269	283,868	137,882
Income from Operations	45,980	26,206	1,103
Identifiable Assets	840,187	814,994	792,953
Goodwill	344,644	344,653	344,678
Capital Expenditures	4,210	4,517	3,236
Depreciation and Amortization	18,139	18,248	6,798
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(1,161)	0	0
Income from Operations	(33)	0	0
Identifiable Assets	$ (33)	$ 0	$ 0