Investments - Contractual Maturities of Marketable Investments (Details) - USD ($) $ in Millions	Sep. 26, 2021	Jun. 27, 2021
Debt Securities, Available-for-sale [Line Items]
Within One Year	$ 124.6
After One, Within Five Years	451.7
After Five, Within Ten Years	0.0
After Ten Years	20.0
Total	596.3	$ 775.6
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Within One Year	27.5
After One, Within Five Years	109.9
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	137.4	141.3
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Within One Year	65.5
After One, Within Five Years	303.8
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	369.3	459.5
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Within One Year	5.5
After One, Within Five Years	8.3
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	13.8	15.8
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Within One Year	16.6
After One, Within Five Years	29.7
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	46.3	72.5
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Within One Year	9.5
After One, Within Five Years	0.0
After Five, Within Ten Years	0.0
After Ten Years	0.0
Total	9.5	16.5
Variable rate demand notes
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	20.0
Total	$ 20.0	$ 20.0