STOCKHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Schedule of Amounts Reclassified Out of Other Comprehensive Earnings (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 29, 2017	Dec. 30, 2016
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Revenues	$ 678.5	$ 601.5
Net earnings (loss) attributable to Varian	(112.3)	13.9
Unrealized loss on defined benefit pension and post-retirement benefit plans
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Cost of revenues & Operating expenses	(0.4)	(0.9)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Net earnings (loss) attributable to Varian	(0.3)	(0.9)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gain on cash flow hedging instruments
Reclassification Adjustment Out Of Accumulated Comprehensive Income [Line Items]
Revenues	$ 0.1	$ 0.0