VPT Loans - CPTC Loans (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Oct. 02, 2015	Jun. 30, 2014	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	$ 95.3	$ 93.0
Available-for-sale Securities:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	$ 95.3	83.9
CPTC loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
CPTC loan facility, amortization period over which monthly payments are calculated after January 1, 2015	15 years
Accounts receivable	$ 32.6	25.2
CPTC loans | LIBOR
Accounts, Notes, Loans and Financing Receivable [Line Items]
CPTC loan facility, interest rate margin (as a percent)	7.00%
CPTC loans | Tranche C Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum commitment	$ 9.7
CPTC loans | Varian Medical Systems, Inc. | Tranche C Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum commitment	$ 4.4
CPTC loans | Available-for-sale Securities:
Accounts, Notes, Loans and Financing Receivable [Line Items]
CPTC loan facility, minimum interest rate during initial term (as a percent)	9.00%
CPTC loans | Available-for-sale Securities: | Tranche A loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum borrowing capacity				$ 165.3
CPTC loans | Available-for-sale Securities: | Varian Medical Systems, Inc. | Tranche A loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum commitment			$ 70.3	$ 115.3
Significant sales			38.1
CPTC loans | Available-for-sale Securities: | Varian Medical Systems, Inc. | Tranche B loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum commitment			10.0
CPTC loans | Available-for-sale Securities: | J.P. Morgan | Tranche A loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sale of portion of commitment			$ 45.0
CPTC loans | Short-term Investments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	$ 95.3
CPTC loans | Short-term Investments | Tranche A loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	80.5
CPTC loans | Short-term Investments | Tranche B loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	11.4
CPTC loans | Short-term Debt | Tranche C Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities	$ 3.4
CPTC loans | Other Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities		83.9
CPTC loans | Other Assets | Tranche A loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities		73.5
CPTC loans | Other Assets | Tranche B loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available-for-sale securities		$ 10.4