Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) by Component, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,159.5
Other comprehensive income (loss)	(1.5)	$ 14.0
Ending balance	1,177.8	1,191.3
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(15.7)	(6.9)
Other comprehensive income (loss) before reclassifications	(1.5)	14.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Other comprehensive income (loss)	(1.5)	14.0
Ending balance	(17.2)	7.1
Unrealized Gains and Losses on Investment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0.0	140.0
Other comprehensive income (loss) before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Other comprehensive income (loss)	0.0	(140.0)
Ending balance	0.0	0.0
Pension Liability Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1.4)	(2.3)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	0.0
Other comprehensive income (loss)	0.0	0.0
Ending balance	(1.4)	(2.3)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(17.1)	130.8
Other comprehensive income (loss)	(1.5)	14.0
Ending balance	(18.6)	4.8
Accounting Standards Update 2016-01 | Unrealized Gains and Losses on Investment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment	0.0	(140.0)
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment	$ 0.0	$ (140.0)