Revenue and Contract Balances - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 27, 2020	Sep. 29, 2019
Disaggregation of Revenue [Line Items]
Contract liability revenue recognized during the period	$ 118,000	$ 90,000
Favorable operating income adjustments	800	800
Liabilities for anticipated losses	13,200	11,500
Estimated cost to complete the related contracts	$ 118,000
Period for billing and collecting unbilled receivables	12 months
Unbilled accounts receivable related to claims and requests for equitable adjustment on contracts	$ 14,000	15,000
Remaining unsatisfied performance obligation	$ 3,218,973
Remaining performance obligation, termination notice period one	30 days
Remaining performance obligation, termination notice period two	60 years
Remaining performance obligation, termination notice period three	90 days
CIG
Disaggregation of Revenue [Line Items]
Losses from claim settlement	$ 4,400	28,200
Reduction in the revenue related to the evaluation of the claims		26,700
RCM
Disaggregation of Revenue [Line Items]
Losses from claim settlement		5,700
Reduction in the revenue related to the evaluation of the claims		$ 4,600