Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended			9 Months Ended
	Jul. 31, 2015 USD ($)	Jul. 03, 2015 USD ($) installment	Jun. 27, 2014 USD ($)	Mar. 28, 2014 USD ($)	Jul. 03, 2015 USD ($) installment	Jun. 27, 2014 USD ($)	Jul. 15, 2015 USD ($)	May. 31, 2015 USD ($) payment	Sep. 26, 2014 USD ($)	Dec. 27, 2013 USD ($)	Apr. 30, 2012 USD ($)
Commitments And Contingencies [Line Items]
Long term accrued product warranty costs		$ 1,700,000			$ 1,700,000				$ 2,000,000
Environmental cleanup costs, third-party claim costs, project management costs and legal costs		200,000	$ 300,000		1,000,000	$ 800,000
Receivables of past and future environmental-related expenditures		2,100,000			2,100,000				2,200,000
Full settlement of the lawsuit to the University of Pittsburgh			35,600,000	$ 35,600,000
Litigation settlement				$ 25,100,000
Prepaid royalties			5,500,000			5,500,000
Loss contingency accrual										$ 5,000,000
Enhanced Retirement Program and Workforce Reduction
Commitments And Contingencies [Line Items]
Restructuring charges			$ 0		13,400,000	$ 0
Payments for restructuring charges					10,900,000
Unfavorable Regulatory Action
Commitments And Contingencies [Line Items]
Loss contingency accrual		0			$ 0
Patents
Commitments And Contingencies [Line Items]
Finite-lived intangible asset, useful life					2 years 6 months
Cercla sites and one past facility
Commitments And Contingencies [Line Items]
Estimated environmental remediation costs, minimum		1,600,000			$ 1,600,000
Estimated environmental remediation costs, maximum		9,800,000			9,800,000
Amount accrued for environmental remediation expense		1,600,000			$ 1,600,000
Cercla sites and one past facility | Minimum
Commitments And Contingencies [Line Items]
Estimated time frames to resolve contingency related to environmental remediation contingencies, years					1 year
Cercla sites and one past facility | Maximum
Commitments And Contingencies [Line Items]
Estimated time frames to resolve contingency related to environmental remediation contingencies, years					30 years
Other sites
Commitments And Contingencies [Line Items]
Estimated environmental remediation costs, minimum		5,000,000			$ 5,000,000
Estimated environmental remediation costs, maximum		35,400,000			35,400,000
Amount accrued for environmental remediation expense		$ 7,400,000			7,400,000
Estimated environmental remediation costs, best estimate, undiscounted					$ 9,000,000
Discount rate for environmental remediation costs, net of inflation		4.00%			4.00%
Other sites | Minimum
Commitments And Contingencies [Line Items]
Estimated time frames to resolve contingency related to environmental remediation contingencies, years					1 year
Other sites | Maximum
Commitments And Contingencies [Line Items]
Estimated time frames to resolve contingency related to environmental remediation contingencies, years					30 years
dpiX LLC
Commitments And Contingencies [Line Items]
Fixed cost commitments		$ 4,400,000			$ 4,400,000
Maryland Proton Therapy Center (MPTC)
Commitments And Contingencies [Line Items]
Financing receivable, maximum lending commitment								$ 35,000,000
Financing receivable, number of annual payments | payment								3
Financing receivable, gross		$ 22,800,000			$ 22,800,000
Financing receivable, outstanding commitment, number of installment payments | installment		4			4
Financing receivable, outstanding commitment, installment payment, amount		$ 5,700,000			$ 5,700,000
MM Proton I, LLC | Subsequent Event
Commitments And Contingencies [Line Items]
Financing receivable, maximum lending commitment	$ 91,500,000
MM Proton I, LLC | Subsequent Event | Financing Receivable, Senior Loan
Commitments And Contingencies [Line Items]
Financing receivable, maximum lending commitment	$ 73,000,000
Financing receivable, term	6 years
MM Proton I, LLC | Subsequent Event | Financing Receivable, Subordinate Loan
Commitments And Contingencies [Line Items]
Financing receivable, maximum lending commitment	$ 18,500,000
Financing receivable, gross							$ 15,500,000
Financing receivable, term	6 years 6 months
Fair Value, Measurements, Recurring
Commitments And Contingencies [Line Items]
Contingent consideration		4,100,000			4,100,000				$ 7,500,000
Siemens AG | Strategic Global Partnership
Commitments And Contingencies [Line Items]
Fixed fee committed		4,500,000			4,500,000						$ 10,000,000
License fee committed		$ 12,000,000			$ 12,000,000						$ 20,000,000