Investments - Marketable Investments by Type (Details) - USD ($) $ in Millions	Jun. 27, 2021	Jun. 28, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 770.5	$ 782.0
Gross Unrealized Gains	5.5	8.9
Gross Unrealized Losses	0.4	0.0
Estimated Fair Value	775.6	790.9
Maximum
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses		0.1
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	139.4	130.0
Gross Unrealized Gains	1.9	2.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	141.3	132.0
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	456.5	473.8
Gross Unrealized Gains	3.3	6.3
Gross Unrealized Losses	0.3	0.0
Estimated Fair Value	459.5	480.1
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15.8	29.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	15.8	29.1
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	72.3	52.3
Gross Unrealized Gains	0.3	0.6
Gross Unrealized Losses	0.1	0.0
Estimated Fair Value	72.5	52.9
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16.5	83.3
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	16.5	83.3
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	50.0	11.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	50.0	11.0
Variable rate demand note
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20.0	2.5
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	$ 20.0	$ 2.5

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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