Accumulated Other Comprehensive Loss (Details) - USD ($)	12 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 30, 2018
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	$ 725,800,000	$ 734,900,000	$ 803,500,000
Other comprehensive (loss) income before reclassification	(34,100,000)
Amounts reclassified from accumulated other comprehensive (loss) income	2,800,000
Net change in accumulated other comprehensive loss	(31,300,000)	(31,700,000)	(10,300,000)
Ending balance	711,400,000	725,800,000	734,900,000
Unrealized actuarial loss	5,700,000
Income tax benefit	300,000
Available-for-sale securities | Lumentum
Changes in accumulated other comprehensive income (loss) by component
Tax impact from reclassification of gross realized gain from available-for-sale securities	0
Total
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(134,600,000)	(102,900,000)	(92,600,000)
Net change in accumulated other comprehensive loss	(31,300,000)	(31,700,000)	(10,300,000)
Ending balance	(165,900,000)	(134,600,000)	$ (102,900,000)
Unrealized gains (losses) on available-for-sale investments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(5,000,000.0)
Other comprehensive (loss) income before reclassification	(100,000)
Amounts reclassified from accumulated other comprehensive (loss) income	0
Net change in accumulated other comprehensive loss	(100,000)
Ending balance	(5,100,000)	(5,000,000.0)
Foreign currency translation adjustments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(101,000,000.0)
Other comprehensive (loss) income before reclassification	(28,600,000)
Amounts reclassified from accumulated other comprehensive (loss) income	0
Net change in accumulated other comprehensive loss	(28,600,000)
Ending balance	(129,600,000)	(101,000,000.0)
Change in unrealized components of defined benefit obligations, net of tax
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(28,600,000)
Other comprehensive (loss) income before reclassification	(5,400,000)
Amounts reclassified from accumulated other comprehensive (loss) income	2,800,000
Net change in accumulated other comprehensive loss	(2,600,000)
Ending balance	$ (31,200,000)	$ (28,600,000)