Business Segment Information (Financial Information by Reportable Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Segment Reporting Information [Line Items]
Revenue	$ 828,586	$ 892,518	$ 778,032
Income from Operations	(247,487)	79,705	65,172
Identifiable Assets	1,150,231	1,297,977	1,139,396
Goodwill	228,640	429,039	369,275
Capital Expenditures	23,893	30,525	12,321
Depreciation and Amortization	46,687	37,975	34,492
Impairment of intangible assets	49,871
Goodwill impairment	241,518
Test & Simulation
Segment Reporting Information [Line Items]
Revenue	490,634	558,908	464,924
Income from Operations	(90,455)	34,080	19,225
Identifiable Assets	442,707	419,403	299,242
Goodwill	48,840	61,153	24,631
Capital Expenditures	10,203	18,792	8,111
Depreciation and Amortization	26,150	19,529	16,353
Restructuring expense	11,848
Impairment of intangible assets	89,814
Goodwill impairment	53,344
Sensors
Segment Reporting Information [Line Items]
Revenue	339,223	334,976	314,269
Income from Operations	(157,030)	45,620	45,980
Identifiable Assets	707,554	878,602	840,187
Goodwill	179,800	367,886	344,644
Capital Expenditures	13,690	11,733	4,210
Depreciation and Amortization	20,537	18,446	18,139
Impairment of intangible assets	201,574
Goodwill impairment	188,174
Intersegment
Segment Reporting Information [Line Items]
Revenue	(1,271)	(1,366)	(1,161)
Income from Operations	(2)	5	(33)
Identifiable Assets	$ (30)	$ (28)	$ (33)