Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended	12 Months Ended
	Oct. 03, 2020 USD ($)	Oct. 03, 2020 USD ($) reporting_unit	Sep. 28, 2019 USD ($)	Sep. 29, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Capitalization of software development costs		$ 13,882,000	$ 8,295,000	$ 5,167,000
Foreign currency transaction gain (loss), before tax		(636,000)	(200,000)	104,000
Amortization expense on capitalized computer software		264,000	176,000	30,000
Impairment of assets		$ 291,389,000	0	0
Number of reporting units | reporting_unit		5
Goodwill impairment		$ 241,518,000
Goodwill	$ 228,640,000	228,640,000	429,039,000	369,275,000
Foreign exchange contracts with credit-risk related contingent features	0	$ 0	0
Trade names
Summary Of Significant Accounting Policies [Line Items]
Impairment of indefinite-lived intangible assets	13,400,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Percent fair value is less than carrying amount		50.00%
Test & Simulation
Summary Of Significant Accounting Policies [Line Items]
Impairment charges of amortizing intangible assets	36,471,000
Legacy Test
Summary Of Significant Accounting Policies [Line Items]
Goodwill impairment	22,509,000
Goodwill	4,011,000	$ 4,011,000
E2M
Summary Of Significant Accounting Policies [Line Items]
Goodwill impairment	30,835,000
Goodwill	7,056,000	7,056,000
PCB
Summary Of Significant Accounting Policies [Line Items]
Goodwill impairment	188,174,000
Goodwill	178,328,000	178,328,000
Temposonics
Summary Of Significant Accounting Policies [Line Items]
Goodwill	1,472,000	1,472,000
Sensors
Summary Of Significant Accounting Policies [Line Items]
Goodwill impairment		188,174,000
Goodwill	179,800,000	179,800,000	367,886,000	$ 344,644,000
R&D
Summary Of Significant Accounting Policies [Line Items]
Capitalization of software development costs		8,403,000	$ 5,883,000
Goodwill	$ 37,773,000	$ 37,773,000