Equity - Components of Accumulated Other Comprehensive (Loss) Income, Net of Tax (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 4,610.6
Balance	4,390.7
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(18.5)
Other comprehensive loss before reclassifications	(42.6)
Amount reclassified from accumulated other comprehensive loss	1.9
Other comprehensive loss, net	(40.7)
Balance	(59.2)
Unrealized Gains/Losses on Available-for- Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	29.7
Other comprehensive loss before reclassifications	(3.0)
Amount reclassified from accumulated other comprehensive loss	0.5
Other comprehensive loss, net	(2.5)
Balance	27.2
Unrealized Gains/Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(4.3)
Other comprehensive loss before reclassifications	(24.9)
Amount reclassified from accumulated other comprehensive loss	1.4
Other comprehensive loss, net	(23.5)
Balance	(27.8)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(43.9)
Other comprehensive loss before reclassifications	(14.7)
Amount reclassified from accumulated other comprehensive loss	0.0
Other comprehensive loss, net	(14.7)
Balance	$ (58.6)