VPT Loans and Securities - MPTC Loan (Details)	12 Months Ended
	Sep. 29, 2017 USD ($) funding_payment	Sep. 30, 2016 USD ($) funding_payment	Oct. 02, 2015 USD ($)	May 31, 2015 USD ($) installment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Payments to Acquire Notes Receivable	$ 18,200,000	$ 21,700,000	$ 23,700,000
Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, net	91,700,000	65,000,000
LT Notes	86,700,000	59,200,000
MPTC loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount				$ 22,800,000
Accounts receivable	0	9,200,000
Unbilled accounts receivable		7,100,000
MPTC loan | Notes Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Payments to Acquire Notes Receivable	$ 11,400,000	$ 11,400,000
MPTC loan | Roll Over Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount				12,200,000
Financing receivable, net				10,000,000
Accrued interest				2,200,000.0
MPTC loan | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commitment				$ 35,000,000.0
Financing Receivable, Number of Equal Funding Payments | funding_payment	2	2
Total number of installments | installment				3
Stated rate (as a percent)	12.00%
LT Notes	$ 60,100,000	$ 40,700,000
Reclassification From Long-Term Accounts Receivable In June 2016 | MPTC loan | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Stated rate (as a percent)	15.00%
Financing Receivable, Deferral	$ 25,000,000
LT Notes	$ 25,100,000