Stockholders' Equity and Noncontrolling Interests - Schedule of Amounts Reclassified Out of Other Comprehensive Earnings (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Jan. 01, 2016	Sep. 29, 2017	Sep. 30, 2016	Oct. 02, 2015
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Revenues	$ 739.0	$ 662.4	$ 655.0	$ 611.8	$ 747.2	$ 642.9	$ 615.2	$ 615.8	$ 2,668.2	$ 2,621.1	$ 2,490.7
Operating expenses									(813.7)	(677.9)	(636.4)
Net earnings attributable to Varian	$ 82.7	$ 90.4	$ 56.1	$ 20.4	$ 117.5	$ 98.8	$ 97.0	$ 89.0	249.6	402.3	411.5
Net Unrealized Gains (Losses) Defined Benefit Pension and Post-Retirement Benefit Plans
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Cost Of Revenues And Operating Expenses									(3.4)	(2.4)	(2.1)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Net earnings attributable to Varian									(3.4)	(4.0)	1.7
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) Cash Flow Hedging Instruments
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Revenues									0.0	(1.0)	3.8
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gains (Losses) Available-for- Sale Securities
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income On Derivatives [Line Items]
Operating expenses									$ 0.0	$ (0.6)	$ 0.0