Investments, Forward Contracts and Fair Value Measurements - Amortized Cost to Fair Value Reconciliation (Details) - USD ($) $ in Millions	Jun. 29, 2019	Jun. 30, 2018
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	$ 0.9	$ 190.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.3)	(1.2)
Estimated Fair Value	0.6	189.6
U.S. treasuries
Available-For-Sale Investments
Amortized Cost/ Carrying Cost		36.0
Gross Unrealized Gains		0.0
Gross Unrealized Losses		(0.1)
Estimated Fair Value		35.9
U.S. agencies
Available-For-Sale Investments
Amortized Cost/ Carrying Cost		13.3
Gross Unrealized Gains		0.0
Gross Unrealized Losses		(0.1)
Estimated Fair Value		13.2
Municipal bonds and sovereign debt instruments
Available-For-Sale Investments
Amortized Cost/ Carrying Cost		2.7
Gross Unrealized Gains		0.0
Gross Unrealized Losses		0.0
Estimated Fair Value		2.7
Asset-backed securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	0.9	23.9
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.3)	(0.4)
Estimated Fair Value	$ 0.6	23.5
Corporate securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost		114.9
Gross Unrealized Gains		0.0
Gross Unrealized Losses		(0.6)
Estimated Fair Value		$ 114.3

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).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount 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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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