Equity - Components of Accumulated Other Comprehensive (Loss) Income, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 4,464.3	$ 4,591.2	$ 4,610.6	$ 4,823.2
Other comprehensive loss before reclassifications			25.7
Amount reclassified from accumulated other comprehensive loss			8.0
Other comprehensive loss, net	38.1	(15.5)	33.7	(8.6)
Balance	4,560.8	4,642.4	4,560.8	4,642.4
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(22.9)	(11.3)	(18.5)	(18.2)
Balance	15.2	$ (26.8)	15.2	$ (26.8)
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			6.2
Amount reclassified from accumulated other comprehensive loss			(0.5)
Other comprehensive loss, net			5.7
Balance	35.4		35.4
Unrealized Gains/Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance			(4.3)
Other comprehensive loss before reclassifications			21.0
Amount reclassified from accumulated other comprehensive loss			8.5
Other comprehensive loss, net			29.5
Balance	25.2		25.2
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance			(43.9)
Other comprehensive loss before reclassifications			(1.5)
Amount reclassified from accumulated other comprehensive loss			0.0
Other comprehensive loss, net			(1.5)
Balance	$ (45.4)		$ (45.4)