Goodwill - Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 30, 2018
Changes in goodwill
Balance at the beginning of the period	$ 381.1	$ 336.3
Acquisitions	4.3	46.1
Other		3.7
Currency translation and other adjustments	(4.0)	(5.0)
Balance at the end of the period	381.4	381.1
Network Enablement
Changes in goodwill
Balance at the beginning of the period	338.9	328.0
Acquisitions	0.0	12.2
Other		3.7
Currency translation and other adjustments	(4.0)	(5.0)
Balance at the end of the period	334.9	338.9
Goodwill balance	636.8	640.8	$ 629.9
Accumulated impairment losses	301.9	301.9	301.9
Service Enablement
Changes in goodwill
Balance at the beginning of the period	0.0	0.0
Acquisitions	4.3	0.0
Other		0.0
Currency translation and other adjustments	0.0	0.0
Balance at the end of the period	4.3	0.0
Goodwill balance	276.9	272.6	272.6
Accumulated impairment losses	272.6	272.6	272.6
Optical Security and Performance Products
Changes in goodwill
Balance at the beginning of the period	42.2	8.3
Acquisitions	0.0	33.9
Balance at the end of the period	42.2	42.2
Goodwill balance	126.7	126.7	92.8
Accumulated impairment losses	$ 84.5	$ 84.5	$ 84.5