Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income by Component, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2018	Apr. 02, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,151.5
Other comprehensive income	14.0	$ 24.6
Ending balance	1,191.3	1,049.7
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6.9)	(23.3)
Other comprehensive income before reclassifications	14.0	5.7
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
Other comprehensive income	14.0	5.7
Ending balance	7.1	(17.6)
Unrealized Gains and Losses on Investment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	140.0	83.8
Other comprehensive income before reclassifications	0.0	18.9
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
Other comprehensive income	(140.0)	18.9
Ending balance	0.0	102.7
Pension Liability Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2.3)	(1.8)
Other comprehensive income before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income	0.0	0.0
Other comprehensive income	0.0	0.0
Ending balance	(2.3)	(1.8)
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	130.8	58.7
Other comprehensive income	14.0	24.6
Ending balance	4.8	83.3
Accounting Standards Update 2016-01 | Unrealized Gains and Losses on Investment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment	(140.0)	0.0
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment	$ (140.0)	$ 0.0