Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended								12 Months Ended
	Jan. 28, 2017	Sep. 29, 2017 USD ($) customer	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) customer	Jul. 01, 2016 USD ($)	Apr. 01, 2016 USD ($)	Jan. 01, 2016 USD ($)	Sep. 29, 2017 USD ($) customer reporting_unit segment	Sep. 30, 2016 USD ($) customer	Oct. 02, 2015 USD ($) customer	Apr. 02, 1999 company
Significant Accounting Policies [Line Items]
Number of reportable segments | segment										2
Number of publicly traded companies | company													3
Number of publicly traded companies distributed to stockholders | company													2
Foreign currency gain (loss) before tax										$ 3,000,000	$ 1,600,000	$ (2,000,000)
Impairment charges										$ 51,400,000	0	0
Number of reporting units tested for impairment of goodwill | reporting_unit										2
Warranty period										12 months
Customer billings in excess of costs incurred and revenue recognized		$ 10,000,000				$ 13,700,000				$ 10,000,000	13,700,000
VPT fair value in excess of carrying amount (percent)		21.00%								21.00%
Decrease to net revenues		$ 739,000,000	$ 662,400,000	$ 655,000,000	$ 611,800,000	747,200,000	$ 642,900,000	$ 615,200,000	$ 615,800,000	$ 2,668,200,000	2,621,100,000	$ 2,490,700,000
Adjustments for New Accounting Pronouncement [Member]
Significant Accounting Policies [Line Items]
Decrease to net revenues										$ (29,000,000)	(9,000,000)
Minimum
Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life (in years)										2 years
Maximum
Significant Accounting Policies [Line Items]
Finite-lived intangible asset, useful life (in years)										10 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
Prepaid expenses and other current assets | Accounting Standards Update 2015-03
Significant Accounting Policies [Line Items]
Unamortized debt issuance costs						(600,000)					(600,000)
Other Assets | Accounting Standards Update 2015-03
Significant Accounting Policies [Line Items]
Unamortized debt issuance costs						$ (600,000)					$ (600,000)
Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Number of customers representing more than 10% | customer		0				0				0	0	0