SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 30, 2018
Accounts receivable allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 4.5	$ 2.6	$ 1.8
Assumed in Oclaro Acquisition	0.0	3.3	0.0
Increase (decrease) to Income Statement	0.1	(0.2)	0.9
Write Offs / Deductions Credited to Expenses or Other Accounts	(2.8)	(1.2)	(0.1)
Balance at End of Period	1.8	4.5	2.6
Deferred tax valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	190.3	99.4	296.4
Additions Charged to Expenses or Other Accounts	16.3	153.9	234.1
Write Offs / Deductions Credited to Expenses or Other Accounts	(5.8)	(63.0)	(431.1)
Balance at End of Period	$ 200.8	$ 190.3	$ 99.4