Derivative Financial Instruments - Effect on Statement of Comprehensive Income and Statement of Income (Details) - Designated as Hedging Instrument - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Derivatives in Net Investment Hedging Relationship
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		$ 15.2	$ (6.4)
Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings		0.1	(0.1)
Gain Recognized in Earnings from Excluded Components	[1]	2.8	3.5
Derivatives in Net Investment Hedging Relationship | Forward contracts
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		65.0	(16.8)
Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings		0.1	(0.1)
Gain Recognized in Earnings from Excluded Components	[1]	2.8	3.5
Derivatives in Net Investment Hedging Relationship | Put options
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		(47.7)	17.9
Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings		0.0	0.0
Gain Recognized in Earnings from Excluded Components	[1]	0.0	0.0
Derivatives in Net Investment Hedging Relationship | Call options
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		(1.3)	(7.5)
Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings		0.0	0.0
Gain Recognized in Earnings from Excluded Components	[1]	0.0	0.0
Cash Flow Hedging | Interest rate swap
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		(0.8)	0.0
Loss Reclassified from Accumulated Other Comprehensive Loss into Earnings		0.0	0.0
Gain Recognized in Earnings from Excluded Components	[1]	$ 0.0	$ 0.0

[1] The excluded components of the forward contracts were recognized in earnings on a straight-line basis over the respective period of the contracts as a reduction to Interest expense on the Consolidated Statements of Income.