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. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Jan. 01, 2016	Oct. 02, 2015	Jul. 03, 2015	Apr. 03, 2015	Jan. 02, 2015	Sep. 30, 2016	Oct. 02, 2015	Sep. 26, 2014
Earnings Per Share [Abstract]
Net earnings attributable to Varian	$ 117.5	$ 98.8	$ 97.0	$ 89.0	$ 98.7	$ 113.5	$ 106.0	$ 93.3	$ 402.3	$ 411.5	$ 403.7
Weighted average shares outstanding - basic (in shares)									95.4	99.7	104.0
Dilutive effect of potential common shares (in shares)									0.6	0.9	1.3
Weighted average shares outstanding - diluted (in shares)									96.0	100.6	105.3
Net earnings per share - basic (in dollars per share)	$ 1.25	$ 1.04	$ 1.01	$ 0.92	$ 1.00	$ 1.14	$ 1.06	$ 0.93	$ 4.22	$ 4.13	$ 3.88
Net earnings per share - diluted (in dollars per share)	$ 1.24	$ 1.04	$ 1.01	$ 0.91	$ 0.99	$ 1.13	$ 1.05	$ 0.92	$ 4.19	$ 4.09	$ 3.83
Anti-dilutive employee shared based awards, excluded (in shares)									1.6	1.0	0.6