Equity - Components of Accumulated Other Comprehensive (Loss) Income, Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 4,543.5	$ 4,610.6
Other comprehensive income (loss) before reclassifications	35.4
Amount reclassified from accumulated other comprehensive income (loss)	(9.7)
Other comprehensive income (loss), net	25.7	(40.7)
Balance	4,429.6	4,390.7
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	55.6	(18.5)
Other comprehensive income (loss), net	25.7	(40.7)
Balance	81.3	$ (59.2)
Unrealized Gains/Losses on Available-for- Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	34.1
Other comprehensive income (loss) before reclassifications	(1.2)
Amount reclassified from accumulated other comprehensive income (loss)	(0.8)
Other comprehensive income (loss), net	(2.0)
Balance	32.1
Unrealized Gains/Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	57.7
Other comprehensive income (loss) before reclassifications	38.5
Amount reclassified from accumulated other comprehensive income (loss)	(8.9)
Other comprehensive income (loss), net	29.6
Balance	87.3
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(36.2)
Other comprehensive income (loss) before reclassifications	(1.9)
Amount reclassified from accumulated other comprehensive income (loss)	0.0
Other comprehensive income (loss), net	(1.9)
Balance	$ (38.1)