Investments, Forward Contracts and Fair Value Measurements - Measured at Fair Value (Details) - USD ($) $ in Millions	Sep. 29, 2018	Jun. 30, 2018
Debt available-for-sale securities
Total debt available-for-sale securities	$ 50.7	$ 189.6
U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	4.0	35.9
Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	8.7	13.2
Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	2.7	2.7
Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	6.7	23.5
Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	28.6	114.3
Recurring basis
Debt available-for-sale securities
Total debt available-for-sale securities	50.7	189.6
Money market funds	329.1	354.9
Trading securities	1.6	1.6
Foreign currency forward contracts	1.9	2.7
Total assets	383.3	548.8
Liability:
Foreign currency forward contracts	3.2	11.7
Total liabilities	3.2	11.7
Recurring basis \| Cash and cash equivalents
Debt available-for-sale securities
Total assets	318.0	364.8
Recurring basis \| Short-term investments
Debt available-for-sale securities
Total assets	51.7	169.3
Recurring basis \| Restricted cash
Debt available-for-sale securities
Total assets	7.1	7.3
Recurring basis \| Prepayments and other current assets
Debt available-for-sale securities
Total assets	1.9
Recurring basis \| Other current assets
Debt available-for-sale securities
Total assets		2.7
Recurring basis \| Other non-current assets
Debt available-for-sale securities
Total assets	4.6	4.7
Recurring basis \| Other current liabilities
Liability:
Total liabilities	3.2	11.7
Recurring basis \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	4.0	35.9
Recurring basis \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	8.7	13.2
Recurring basis \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	2.7	2.7
Recurring basis \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	6.7	23.5
Recurring basis \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	28.6	114.3
Recurring basis \| Level 1 Investments
Debt available-for-sale securities
Total debt available-for-sale securities	4.0	35.9
Money market funds	329.1	354.9
Trading securities	1.6	1.6
Foreign currency forward contracts	0.0	0.0
Total assets	334.7	392.4
Liability:
Foreign currency forward contracts	0.0	0.0
Total liabilities	0.0	0.0
Recurring basis \| Level 1 Investments \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	4.0	35.9
Recurring basis \| Level 1 Investments \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis \| Level 1 Investments \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis \| Level 1 Investments \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis \| Level 1 Investments \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis \| Level 2 Investments
Debt available-for-sale securities
Total debt available-for-sale securities	46.7	153.7
Money market funds	0.0	0.0
Trading securities	0.0	0.0
Foreign currency forward contracts	1.9	2.7
Total assets	48.6	156.4
Liability:
Foreign currency forward contracts	3.2	11.7
Total liabilities	3.2	11.7
Recurring basis \| Level 2 Investments \| U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis \| Level 2 Investments \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	8.7	13.2
Recurring basis \| Level 2 Investments \| Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	2.7	2.7
Recurring basis \| Level 2 Investments \| Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	6.7	23.5
Recurring basis \| Level 2 Investments \| Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	$ 28.6	$ 114.3

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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