Revenue and Contract Balances - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019	Sep. 29, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract liability revenue recognized during the period		$ 106,000	$ 84,000
Favorable (unfavorable) operating income adjustments	$ 8,200	(2,800)	5,000
Liabilities for anticipated losses		19,500		$ 11,500
Estimated cost to complete the related contracts		$ 96,000
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		$ 3,049,933
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
RCM
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Recognized reduction of revenue			4,800
Losses from claim settlement			5,900
CIG
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Recognized reduction of revenue			4,200
Losses from claim settlement		$ 4,400	$ 4,200