Derivatives - Undesignated Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash Flow and Fair Value Hedges
Foreign exchange gains/(losses) on settlement assets and obligations, cash balances, and other assets and liabilities	$ 3.0	$ (4.3)	$ (48.0)	$ (15.1)
Not designated as hedges
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives	(3.1)	1.0	26.1	7.8
Not designated as hedges | Selling, general and administrative
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives	$ (3.1)	$ 1.0	$ 26.1	7.6
Not designated as hedges | Revenue
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives				$ 0.2