Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Period Type:	duration

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Earnings Per Share - Computation of Net Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 70.4	$ 29.5	$ 88.4	$ 103.9	$ 116.8	$ 72.5	$ 73.2	$ (112.2)	$ 292.2	$ 150.3	$ 226.0
Less: Net earnings from continuing operations attributable to noncontrolling interests									0.3	0.4	0.6
Net earnings from continuing operations attributable to Varian									291.9	149.9	225.4
Net loss from discontinued operations									0.0	0.0	(6.8)
Less: Net earnings from discontinued operations attributable to noncontrolling interests									0.0	0.0	0.1
Net loss from discontinued operations attributable to Varian									0.0	0.0	(6.9)
Net earnings attributable to Varian	$ 70.7	$ 29.4	$ 88.6	$ 103.2	$ 116.4	$ 72.6	$ 73.2	$ (112.3)	$ 291.9	$ 149.9	$ 218.5
Weighted average shares outstanding - basic (in shares)									91.0	91.5	92.5
Dilutive effect of potential common shares (in shares)									0.9	1.0	0.7
Weighted average shares outstanding - diluted (in shares)									91.9	92.5	93.2
Net earnings (loss) per share from continuing operations - basic (in dollars per share)									$ 3.21	$ 1.64	$ 2.44
Net earnings (loss) per share from discontinued operations - basic (in dollars per share)									0	0	(0.08)
Net earnings per share - basic (in dollars per share)	$ 0.78	$ 0.32	$ 0.97	$ 1.13	$ 1.27	$ 0.79	$ 0.80	$ (1.22)	3.21	1.64	2.36
Net earnings (loss) per share from continuing operations - diluted (in dollars per share)									3.18	1.62	2.42
Net earnings (loss) per share from discontinued operations - diluted (in dollars per share)									0	0	(0.07)
Net earnings per share - diluted (in dollars per share)	$ 0.77	$ 0.32	$ 0.96	$ 1.12	$ 1.26	$ 0.79	$ 0.79	$ (1.22)	$ 3.18	$ 1.62	$ 2.35
Anti-dilutive employee shared based awards, excluded (in shares)									0.9	0.7	0.2