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		9 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 72.5	$ 69.9	$ 33.5	$ 147.4
Less: Net (loss) earnings from continuing operations attributable to noncontrolling interests	(0.1)	0.2	0.0	0.6
Net earnings from continuing operations attributable to Varian	72.6	69.7	33.5	146.8
Net loss from discontinued operations	0.0	0.0	0.0	(6.8)
Less: Net earnings from discontinued operations attributable to noncontrolling interests	0.0	0.0	0.0	0.1
Net loss from discontinued operations attributable to Varian	0.0	0.0	0.0	(6.9)
Net earnings attributable to Varian	$ 72.6	$ 69.7	$ 33.5	$ 139.9
Weighted average shares outstanding - basic (in shares)	91.5	91.7	91.6	92.7
Dilutive effect of potential common shares (in shares)	1.0	0.7	1.0	0.8
Weighted average shares outstanding - diluted (in shares)	92.5	92.4	92.6	93.5
Net earnings (loss) per share - basic
Continuing operations (in dollars per share)	$ 0.79	$ 0.76	$ 0.37	$ 1.58
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.08)
Net earnings (loss) per share - basic (in dollars per share)	0.79	0.76	0.37	1.50
Net earnings (loss) per share - diluted
Continuing operations (in dollars per share)	0.79	0.75	0.36	1.57
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.07)
Net earnings (loss) per share - diluted (in dollars per share)	$ 0.79	$ 0.75	$ 0.36	$ 1.50
Anti-dilutive employee shared based awards, excluded (in shares)	0.7	0.1	0.7	0.5