SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Out of Period Adjustments (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 29, 2019	Dec. 28, 2018	Mar. 30, 2018	Mar. 29, 2019	Mar. 30, 2018	Sep. 29, 2018	Sep. 28, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Adjustment of income attributable to Varex, net of tax	$ (5.8)		$ (12.2)	$ (8.8)	$ (23.6)
Retained earnings	67.7			67.7		$ 58.9	$ 62.4
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Adjustment of income attributable to Varex, before tax	1.5	$ 1.1
Adjustment of income attributable to Varex, net of tax	1.1	$ 0.6
Adjustment Due to ASC 606 | Accounting Standards Update 2014-09
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings						$ (3.5)
Adjustment Due to ASC 606 | Correction Of ASC 606 Adoption | Accounting Standards Update 2014-09
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings	$ 0.6			$ 0.6