SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Product Warranty (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 29, 2019	Sep. 29, 2018	Sep. 28, 2018
Product Warranty Liability [Line Items]
Retained earnings	$ 67.7	$ 58.9	$ 62.4
Movement in Standard Product Warranty Accrual [Roll Forward]
Accrued product warranty, September 28, 2018	7.3
Charged to cost of revenues	5.2
Product warranty expenditures	(5.7)
Accrued product warranty, March 29, 2019	$ 6.8
Minimum
Product Warranty Liability [Line Items]
Warranty term	12 months
Maximum
Product Warranty Liability [Line Items]
Warranty term	24 months