SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adjustments from Amounts Previously Reported (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Oct. 02, 2015	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Sep. 30, 2017	Sep. 29, 2017
Revenues:
Product		$ 365.0	$ 320.2	$ 1,124.4	$ 994.3
Service		344.1	312.6	993.1	903.2
Total revenues		709.1	632.8	2,117.5	1,897.5
Cost of revenues:
Product		242.5	225.6	730.6	678.7
Service		153.0	141.7	452.0	410.7
Total cost of revenues		395.5	367.3	1,182.6	1,089.4
Gross margin		313.6	265.5	934.9	808.1
Earnings from continuing operations before taxes		92.0	88.7	310.1	198.4
Taxes on earnings		19.5	18.8	276.6	51.0
Net earnings from continuing operations		72.5	69.9	33.5	147.4
Net loss from discontinued operations		0.0	0.0	0.0	(6.8)
Net earnings		72.5	69.9	33.5	140.6
Net earnings attributable to Varian		$ 72.6	$ 69.7	$ 33.5	$ 139.9
Diluted net earnings per share from continuing operations attributable to Varian (in dollars per share)		$ 0.79	$ 0.75	$ 0.36	$ 1.57
Assets:
Trade and unbilled receivables, net		$ 933.6		$ 933.6			$ 961.5
Inventories		469.2		469.2			417.7
Prepaid expenses and other current assets		249.8		249.8			190.3
Deferred tax assets		106.4		106.4			147.3
Liabilities and Equity:
Accrued liabilities		379.0		379.0			374.9
Deferred revenues		790.2		790.2			755.4
Other long-term liabilities		291.2		291.2			127.4
Retained earnings		$ 704.6		$ 704.6			778.6
As Previously Reported
Revenues:
Product			$ 383.4		$ 1,113.1
Service			279.0		816.1
Total revenues			662.4		1,929.2
Cost of revenues:
Product			248.4		727.0
Service			120.7		357.9
Total cost of revenues			369.1		1,084.9
Gross margin			293.3		844.3
Earnings from continuing operations before taxes			116.5		234.6
Taxes on earnings			25.9		60.2
Net earnings from continuing operations			90.6		174.4
Net loss from discontinued operations			0.0		(6.8)
Net earnings			90.6		167.6
Net earnings attributable to Varian			$ 90.4		$ 166.9
Diluted net earnings per share from continuing operations attributable to Varian (in dollars per share)			$ 0.98		$ 1.86
Assets:
Trade and unbilled receivables, net							823.5
Inventories							439.7
Prepaid expenses and other current assets							199.8
Deferred tax assets							138.8
Liabilities and Equity:
Accrued liabilities							394.7
Deferred revenues							640.6
Other long-term liabilities							130.0
Retained earnings							756.0
Adjustments | Accounting Standards Update 2014-09
Revenues:
Product			$ (63.2)		$ (118.8)
Service			33.6		87.1
Total revenues			(29.6)		(31.7)
Cost of revenues:
Product			(22.8)		(48.3)
Service			21.0		52.8
Total cost of revenues			(1.8)		4.5
Gross margin			(27.8)		(36.2)
Earnings from continuing operations before taxes			(27.8)		(36.2)
Taxes on earnings			(7.1)		(9.2)
Net earnings from continuing operations			(20.7)		(27.0)
Net loss from discontinued operations			0.0		0.0
Net earnings			(20.7)		(27.0)
Net earnings attributable to Varian			$ (20.7)		$ (27.0)
Diluted net earnings per share from continuing operations attributable to Varian (in dollars per share)			$ (0.23)		$ (0.29)
Assets:
Trade and unbilled receivables, net							138.0
Inventories							(22.0)
Prepaid expenses and other current assets							(9.5)
Deferred tax assets							8.5
Liabilities and Equity:
Accrued liabilities							(19.8)
Deferred revenues							114.8
Other long-term liabilities							(2.6)
Retained earnings							$ 22.6
Retained Earnings | Accounting Standards Update 2016-09, Forfeiture Rate [Member]
Liabilities and Equity:
Reduction to beginning retained earnings due to election to recognize forfeitures as they occur						$ 0.4
Difference between Revenue Guidance in Effect before and after Topic 606
Liabilities and Equity:
Cumulative effect of ASC 606 to retained earnings	$ 56.7