Investments, Forward Contracts and Fair Value Measurements - Measured at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jul. 01, 2017
Other current liabilities
Liability:
Total liabilities	$ 0.9	$ 1.3
Recurring basis | Cash and cash equivalents
Debt available-for-sale securities
Total assets	588.7	789.2
Recurring basis | Short-term investments
Debt available-for-sale securities
Total assets	430.9	432.2
Recurring basis | Restricted cash
Debt available-for-sale securities
Total assets	7.3	11.0
Recurring basis | Prepayments and other current assets
Debt available-for-sale securities
Total assets	4.0
Recurring basis | Other current assets
Debt available-for-sale securities
Total assets		7.3
Recurring basis | Other non-current assets
Debt available-for-sale securities
Total assets	5.0	5.1
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Debt available-for-sale securities
Total debt available-for-sale securities	88.4	56.7
Money market funds	530.5	726.4
Trading securities	2.1	2.0
Foreign currency forward contracts	0.0	0.0
Total assets	621.0	785.1
Liability:
Foreign currency forward contracts	0.0	0.0
Total liabilities	0.0	0.0
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	88.4	56.7
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Certificates of deposit
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Significant Other Observable Inputs (Level 2)
Debt available-for-sale securities
Total debt available-for-sale securities	410.9	452.4
Money market funds	0.0	0.0
Trading securities	0.0	0.0
Foreign currency forward contracts	4.0	7.3
Total assets	414.9	459.7
Liability:
Foreign currency forward contracts	0.9	1.3
Total liabilities	0.9	1.3
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	0.0
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	13.8	44.9
Recurring basis | Significant Other Observable Inputs (Level 2) | Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	4.4	4.4
Recurring basis | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	62.3	71.1
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	330.4	326.0
Recurring basis | Significant Other Observable Inputs (Level 2) | Certificates of deposit
Debt available-for-sale securities
Total debt available-for-sale securities	0.0	6.0
Recurring basis | Total
Debt available-for-sale securities
Total debt available-for-sale securities	499.3	509.1
Money market funds	530.5	726.4
Trading securities	2.1	2.0
Foreign currency forward contracts	4.0	7.3
Total assets	1,035.9	1,244.8
Liability:
Foreign currency forward contracts	0.9	1.3
Total liabilities	0.9	1.3
Recurring basis | Total | U.S. treasuries
Debt available-for-sale securities
Total debt available-for-sale securities	88.4	56.7
Recurring basis | Total | U.S. agencies
Debt available-for-sale securities
Total debt available-for-sale securities	13.8	44.9
Recurring basis | Total | Municipal bonds and sovereign debt instruments
Debt available-for-sale securities
Total debt available-for-sale securities	4.4	4.4
Recurring basis | Total | Asset-backed securities
Debt available-for-sale securities
Total debt available-for-sale securities	62.3	71.1
Recurring basis | Total | Corporate securities
Debt available-for-sale securities
Total debt available-for-sale securities	330.4	326.0
Recurring basis | Total | Certificates of deposit
Debt available-for-sale securities
Total debt available-for-sale securities	$ 0.0	$ 6.0