Revenue and Contract Balances - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 27, 2021	Mar. 29, 2020	Jun. 27, 2021	Jun. 28, 2020	Sep. 27, 2020
Disaggregation of Revenue [Line Items]
Contract liability revenue recognized during the period			$ 108,000	$ 106,000
Net favorable (unfavorable) operating income adjustments	$ 1,700	$ (2,800)	2,800	(2,800)
Liabilities for anticipated losses	8,000		8,000		$ 13,200
Estimated cost to complete the related contracts	81,000		$ 81,000		118,000
Period for billing and collecting unbilled receivables			12 months
Decline in allowance for doubtful accounts			$ 3,800
Unbilled accounts receivable related to claims and requests for equitable adjustment on contracts	11,000		11,000		$ 11,000
Remaining unsatisfied performance obligation	$ 3,231,133		$ 3,231,133
Remaining performance obligation, termination notice period one			30 days
Remaining performance obligation, termination notice period two			60 days
Remaining performance obligation, termination notice period three			90 days
CIG
Disaggregation of Revenue [Line Items]
Gains (losses) due to change in contract value			$ 2,800	$ (4,400)