Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Total 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
Gross margin	311.3	293.3	275.3	275.7	318.8	283.5	258.1	252.5	1,155.6	1,112.9	1,032.1
Net earnings from continuing operations	82.7	90.6	69.3	14.5	94.3	81.9	77.2	71.9	257.1	325.3	311.4
Net earnings (loss) from discontinued operations	0.0	0.0	(13.3)	6.5	23.5	17.0	19.8	17.1	(6.8)	77.4	100.6
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 earnings (loss) per share from continuing operations - basic (in dollars per share)	$ 0.90	$ 0.99	$ 0.75	$ 0.15	$ 1.00	$ 0.86	$ 0.81	$ 0.74	$ 2.78	$ 3.41	$ 3.13
Net earnings (loss) per share from discontinued operations - basic (in dollars per share)	0.00	0.00	(0.15)	0.07	0.25	0.18	0.20	0.18	(0.08)	0.81	1.00
Net earnings per share - basic (in dollars per share)	0.90	0.99	0.60	0.22	1.25	1.04	1.01	0.92	2.70	4.22	4.13
Net earnings (loss) per share from continuing operations - diluted (in dollars per share)	0.89	0.98	0.74	0.15	1.00	0.86	0.80	0.74	2.75	3.39	3.10
Net earnings (loss) per share from discontinued operations - diluted (in dollars per share)	0.00	0.00	(0.14)	0.07	0.24	0.18	0.21	0.17	(0.07)	0.80	0.99
Net earnings per share - diluted (in dollars per share)	$ 0.89	$ 0.98	$ 0.60	$ 0.22	$ 1.24	$ 1.04	$ 1.01	$ 0.91	$ 2.68	$ 4.19	$ 4.09
Impairment charges	$ 13.1			$ 38.3					$ 51.4	$ 2.2	$ 0.0
Provision for doubtful accounts receivable				$ 37.8					$ 43.7	$ 3.5	$ 1.1