Investments - Contractual Maturities of Marketable Investments (Details) - USD ($) $ in Millions	Mar. 29, 2020	Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Within One Year	$ 280.0
After One, Within Five Years	247.4
After Five, Within Ten Years	0.0
After Ten Years	2.5
Total	529.9	$ 550.9
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Within One Year	15.8
After One, Within Five Years	59.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	74.8	78.5
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Within One Year	158.7
After One, Within Five Years	155.3
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	314.0	257.0
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Within One Year	10.5
After One, Within Five Years	11.1
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	21.6	25.6
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Within One Year	48.6
After One, Within Five Years	21.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	69.6	92.5
Certificates of deposit | Non-US
Debt Securities, Available-for-sale [Line Items]
Within One Year	31.5
After One, Within Five Years	1.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	32.5	50.2
Certificates of deposit | United States
Debt Securities, Available-for-sale [Line Items]
Within One Year	5.2
After One, Within Five Years	0.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	5.2	22.4
Variable rate demand note
Debt Securities, Available-for-sale [Line Items]
Within One Year	0.0
After One, Within Five Years	0.0
After Five, Within Ten Years	0.0
After Ten Years	2.5
Total	2.5	16.9
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Within One Year	9.7
After One, Within Five Years	0.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	$ 9.7	$ 7.8