Commitments and Contingencies - Guarantees and Outstanding Letters of Credit and Performance Bonds (Details) - USD ($) $ in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Mar. 31, 2018	Jun. 29, 2019	Jun. 30, 2018	Jul. 01, 2017
Loss Contingencies [Line Items]
Guarantee liabilities					$ 0.0						$ 0.0
Charge to discontinued operations	$ 0.0	$ 0.0	$ 2.4	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 2.4	$ 0.0	$ (1.6)
Standby letters of credit
Loss Contingencies [Line Items]
Contingency	7.4									7.4
Performance bonds
Loss Contingencies [Line Items]
Contingency	$ 1.5									$ 1.5
Spinoff | Lumentum
Loss Contingencies [Line Items]
Charge to discontinued operations			$ 2.4