Investments and Fair Value Measurements (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jan. 02, 2016	Dec. 27, 2014	Jan. 02, 2016	Dec. 27, 2014	Aug. 01, 2015	Jun. 27, 2015
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	$ 442.2		$ 442.2			$ 496.6
Gross Unrealized Gains	157.2		157.2			0.1
Gross Unrealized Losses	(0.7)		(0.7)			(0.3)
Fair Value	598.7		$ 598.7			496.4
Term of maturities of securities classified as current assets included in short-term investments			12 months
Other-than-temporary impairment loss	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Lumentum
Available-For-Sale Investments
Shares held in investment (in shares)	11.7		11.7		11.7
Cash equivalents
Available-For-Sale Investments
Fair Value	$ 15.8		$ 15.8			33.7
Short-term investments
Available-For-Sale Investments
Fair Value	324.7		324.7			461.9
Other non-current assets
Available-For-Sale Investments
Fair Value	0.7		0.7			0.8
Debt securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	341.9		341.9
Gross Unrealized Gains	0.0		0.0
Gross Unrealized Losses	(0.7)		(0.7)
Fair Value	341.2		341.2
Contractual maturities of debt securities classified as available-for-sale securities, Amortized Cost/Carrying Cost
Amortized cost of amounts maturing in less than 1 year	233.9		233.9
Amortized cost of amounts maturing in 1-5 years	105.5		105.5
Amortized cost of amounts maturing in more than 5 years	2.5		2.5
Total amortized cost of debt available-for-sale securities	341.9		341.9
Contractual maturities of the debt securities classified as available-for-sale securities, Estimated Fair Value
Estimated fair value amounts maturing in less than 1 year	233.8		233.8
Estimated fair value amounts maturing in 1 -5 years	105.3		105.3
Estimated fair value amounts maturing in more than 5 years	2.1		2.1
Total estimated fair value of debt available-for-sale securities	341.2		341.2
U.S. treasuries
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	46.3		46.3			51.9
Gross Unrealized Gains	0.0		0.0			0.0
Gross Unrealized Losses	0.0		0.0			0.0
Fair Value	46.3		46.3			51.9
U.S. agencies
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	59.7		59.7			96.0
Gross Unrealized Gains	0.0		0.0			0.0
Gross Unrealized Losses	(0.1)		(0.1)			0.0
Fair Value	59.6		59.6			96.0
Municipal bonds and sovereign debt instruments
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	2.3		2.3			4.0
Gross Unrealized Gains	0.0		0.0			0.0
Gross Unrealized Losses	0.0		0.0			0.0
Fair Value	2.3		2.3			4.0
Asset-backed securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	49.8		49.8			70.6
Gross Unrealized Gains	0.0		0.0			0.0
Gross Unrealized Losses	(0.4)		(0.4)			(0.2)
Fair Value	49.4		49.4			70.4
Corporate securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	183.8		183.8			274.1
Gross Unrealized Gains	0.0		0.0			0.1
Gross Unrealized Losses	(0.2)		(0.2)			(0.1)
Fair Value	183.6		183.6			$ 274.1
Marketable equity securities
Available-For-Sale Investments
Amortized Cost/ Carrying Cost	100.3		100.3
Gross Unrealized Gains	157.2		157.2
Gross Unrealized Losses	0.0		0.0
Fair Value	257.5		257.5
Marketable equity securities | Short-term investments
Available-For-Sale Investments
Fair Value	$ 257.5		$ 257.5