Derivatives - Undesignated Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flow and Fair Value Hedges
Foreign exchange gains/(losses) on settlement assets and obligations, cash balances, and other assets and liabilities	$ (51.0)	$ (10.8)
Not designated as hedges
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives	29.2	6.8
Not designated as hedges | Selling, general and administrative
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives	$ 29.2	6.6
Not designated as hedges | Revenue
Cash Flow and Fair Value Hedges
Gain/(Loss) recognized in Income on Foreign currency derivatives		$ 0.2