Basis of Presentation and Preparation - Cash and Cash Equivalents and Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Oct. 01, 2017
Cash and Cash Equivalents
Maximum term of original maturity to classify instrument as cash equivalent	90 days
Restricted cash included in "Prepaid expenses and other current assets"	$ 2.7	$ 2.7
Accounts Receivable - Net
Period for billing and collecting unbilled receivables	12 months
Period for earning majority of billings in excess of costs	12 months