Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended			12 Months Ended
	Jan. 28, 2017	Jun. 28, 2019 USD ($)	Jun. 29, 2018 USD ($)	Mar. 30, 2018 USD ($)	Sep. 27, 2019 USD ($) customer specialty_hospital	Sep. 28, 2018 USD ($) customer	Sep. 29, 2017 USD ($) customer	Sep. 28, 2019 USD ($)	Apr. 02, 1999 company
Significant Accounting Policies [Line Items]
Capitalized software development costs for software sold to customers					$ 0
Number of publicly traded companies | company									3
Number of publicly traded companies distributed to stockholders | company									2
Impairment charges					0	$ 0	$ 51,400,000
Impairment of notes receivable			$ 11,000,000.0	$ 11,100,000	$ 50,600,000	22,400,000	51,400,000
Warranty period					12 months
Impairment of long-lived assets					$ 0	0	0
Impairment of identifiable intangible assets					0	0	0
Impairment of goodwill		$ 50,500,000			$ 50,500,000	$ 0	$ 0
Minimum
Significant Accounting Policies [Line Items]
Manufacturing, Commissioning and Installation Period					18 months
Finite-lived intangible asset, useful life (in years)					2 years
Maximum
Significant Accounting Policies [Line Items]
Manufacturing, Commissioning and Installation Period					24 months
Finite-lived intangible asset, useful life (in years)					23 years
Land Improvements
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)					15 years
Building | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)					20 years
Building | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)					30 years
Machinery and Equipment | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)					3 years
Machinery and Equipment | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life (in years)					7 years
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Varex Imaging
Significant Accounting Policies [Line Items]
Number of new shares distributed for every existing share (shares)	0.4
Accounts Receivable
Significant Accounting Policies [Line Items]
Number of customers representing more than 10% | customer					0	0	0
Notes Receivable
Significant Accounting Policies [Line Items]
Impairment of notes receivable						$ 22,100,000
India
Significant Accounting Policies [Line Items]
Number of multi-disciplinary cancer centers | specialty_hospital					9
Number of specialty hospitals | specialty_hospital					1
Sri Lanka
Significant Accounting Policies [Line Items]
Number of multi-disciplinary cancer centers | specialty_hospital					1
Forecast | Minimum | Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Right-of-use assets								$ 119,000,000
Lease liabilities								117,000,000
Forecast | Maximum | Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Right-of-use assets								140,000,000
Lease liabilities								$ 135,000,000
Hardware
Significant Accounting Policies [Line Items]
Warranty period					1 year