Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions		6 Months Ended
	Aug. 01, 2015	Jan. 02, 2016
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period		$ (48.0)
Transfer to Lumentum	$ (7.8)	(7.8)
Other comprehensive (loss) income before reclassification		131.3
Amounts reclassified from accumulated other comprehensive income (loss)		0.3
Net current-period other comprehensive (loss) income		131.6
Balance at the end of the period		75.8
Tax impact of amortization of actuarial losses		0.0
Marketable equity securities | Lumentum
Changes in accumulated other comprehensive income (loss) by component
Unrealized gain on marketable equity securities		157.2
Income tax expense impact from unrealized holding gains on marketable equity securities		3.7
Unrealized gains (losses) on available-for-sale investments
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period		(3.2)
Transfer to Lumentum		0.0
Other comprehensive (loss) income before reclassification		153.1
Amounts reclassified from accumulated other comprehensive income (loss)		0.0
Net current-period other comprehensive (loss) income		153.1
Balance at the end of the period		149.9
Foreign currency translation adjustments
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period		(29.2)
Transfer to Lumentum		(8.9)
Other comprehensive (loss) income before reclassification		(21.8)
Amounts reclassified from accumulated other comprehensive income (loss)		0.0
Net current-period other comprehensive (loss) income		(21.8)
Balance at the end of the period		(59.9)
Defined benefit obligation, net of tax
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period		(15.6)
Transfer to Lumentum		1.1
Other comprehensive (loss) income before reclassification		0.0
Amounts reclassified from accumulated other comprehensive income (loss)		0.3
Net current-period other comprehensive (loss) income		0.3
Balance at the end of the period		$ (14.2)