Proton Solutions Loans and Investments - Additional Information (Details) € in Millions, $ in Millions	1 Months Ended			9 Months Ended	12 Months Ended			13 Months Ended
	Dec. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Jul. 31, 2017 EUR (€)	Jun. 28, 2019 USD ($)	Sep. 27, 2019 USD ($)	Sep. 28, 2018 USD ($)	Sep. 29, 2017 USD ($)	Jul. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of outstanding senior secured debt					$ 0.0	$ 0.0	$ 24.5
Fair Value					58.8	62.5
Investment in available-for-sale securities					0.0	17.8	13.4
Sale of available-for-sale securities					8.5	15.9	$ 0.0
Proton Center, Munich | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of outstanding senior secured debt		$ 24.5	€ 21.5
RPTC securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Claims filed against all of RPTC's assets | €			€ 77.0
Accounts receivable					4.6	4.5
RPTC securities | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term					$ 23.5	24.9
Georgia Proton Therapy Center
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable						0.0
Available-for-sale Securities | Georgia Proton Therapy Center
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investment in available-for-sale securities								$ 16.1
Sale of available-for-sale securities				$ 16.8
APTC Securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable						$ 0.0
Stated rate (as a percent)					8.50%
Investment in available-for-sale securities	$ 6.0
Unbilled accounts receivable					$ 2.1