Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Oct. 02, 2020	Jul. 03, 2020	Apr. 03, 2020	Jan. 03, 2020	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 76.5	$ 60.9	$ 43.1	$ 88.9	$ 70.4	$ 29.5	$ 88.4	$ 103.9	$ 269.4	$ 292.2	$ 150.3
Less: Net earnings from continuing operations attributable to noncontrolling interests									0.2	0.3	0.4
Net earnings from continuing operations attributable to Varian									$ 269.2	$ 291.9	$ 149.9
Weighted average shares outstanding - basic (in shares)									90.9	91.0	91.5
Dilutive effect of potential common shares (in shares)									0.6	0.9	1.0
Weighted average shares outstanding - diluted (in shares)									91.5	91.9	92.5
Net earnings per share - basic (in dollars per share)	$ 0.84	$ 0.67	$ 0.48	$ 0.97	$ 0.78	$ 0.32	$ 0.97	$ 1.13	$ 2.96	$ 3.21	$ 1.64
Net earnings per share - diluted (in dollars per share)	$ 0.83	$ 0.67	$ 0.47	$ 0.96	$ 0.77	$ 0.32	$ 0.96	$ 1.12	$ 2.94	$ 3.18	$ 1.62
Anti-dilutive employee shared based awards, excluded (in shares)									0.7	0.9	0.7