Income Taxes, Provision and Effective tax rate (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Taxes
Provision for income taxes	$ (46.0)	$ (79.6)
Effective tax rate (as a percent)	15.90%	22.80%
Discrete income tax benefit, tax on foreign income	$ 19.9
Discrete income tax benefit, tax on foreign income	(6.90%)
Excess tax benefit from option exercises	$ 5.0	$ 6.8
Excess tax benefit, impact on effective tax rate (in basis points)	(1.70%)	(1.90%)