Financing (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2020	Sep. 28, 2019	Oct. 03, 2020	Sep. 28, 2019	Dec. 28, 2019
Line of Credit Facility [Line Items]
Percent added to Adjusted LIBOR rate for one month interest period			1.00%
Commitment fees incurred on credit facility			$ 341,000	$ 281,000
Annual excess cash flow percentage			50.00%
Net cash proceed percentage			100.00%
Alternate Base Rate
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			2.25%
Minimum
Line of Credit Facility [Line Items]
Commitment fee percentage			0.20%
Minimum | Alternate Base Rate
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			1.75%
Maximum
Line of Credit Facility [Line Items]
Commitment fee percentage			0.45%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity			$ 200,000,000
Maximum borrowing capacity		$ 150,000,000	200,000,000	150,000,000	$ 200,000,000
Debt issuance costs			$ 577,000
Maximum coverage ratio			6.0
Interest coverage ratio			3.0
Long-term Line of Credit		0	$ 75,576,000	0
Letters of credit outstanding, amount		21,173,000	27,895,000	21,173,000
Line of credit facility, remaining borrowing capacity		128,827,000	$ 96,529,000	128,827,000
Revolving Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Repayments of lines of credit	$ 7,000
Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt interest rate spread			1.00%
Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 60,000,000		$ 60,000,000	$ 50,000,000
Term Loan B Facility
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity			$ 460,000,000
Debt instrument, amortization percentage		1.00%	1.00%	1.00%
Line of credit facility, interest rate at period end (in hundredths)			4.53%
Interest rate, percentage			1.00%
Eurocurrency Term Loans
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			3.25%
Eurocurrency Term Loans | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			0.75%
Eurocurrency Term Loans | Minimum | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			0.75%
Eurocurrency Revolving Loans
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)			3.25%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, interest rate at period end (in hundredths)			4.09%
Test & Simulation
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount			$ 30,114,000
Guarantees			$ 39,629,000
5.75% Senior Unsecured Notes Due 2027 | Unsecured Debt
Line of Credit Facility [Line Items]
Principal amount		$ 350,000,000		$ 350,000,000
Interest rate, percentage		5.75%		5.75%
Proceeds from debt, net of issuance costs		$ 343,352,000
Repurchase percentage of principal amount due to change of control		101.00%		101.00%
Repurchase percentage of principal amount due to sale of assets		100.00%		100.00%