Accounts Receivable and Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Oct. 02, 2016
Financial information concerning reportable segments
Period for billing and collecting unbilled receivables	12 months
Period for earning majority of billings in excess of costs	12 months
Unbilled accounts receivable related to claims and requests for equitable adjustment on contracts	$ 74.0	$ 59.0
Billed accounts receivable related to U.S. federal government contracts	81.5	45.4
U.S. federal government unbilled receivables	102.7	109.7
Net unfavorable operating income adjustments		8.0	$ 2.3
Liability for anticipated losses	13.6	8.1
Estimated cost to complete the related contracts	16.4
CIG
Financial information concerning reportable segments
Reduction in the revenue related to the evaluation of the claims	10.6
Loss from claim settlement	12.5
Net unfavorable operating income adjustments	$ 11.2	2.3
RCM
Financial information concerning reportable segments
Reduction in the revenue related to the evaluation of the claims		4.9
Loss from claim settlement		3.6
Net unfavorable operating income adjustments		$ 5.7