Income Taxes, Provision and Effective tax rate (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Taxes
Provision for income taxes	$ (68.0)	$ (78.7)	$ (114.0)	$ (158.3)
Effective tax rate (as a percent)	20.70%	21.30%	18.50%	22.00%
Discrete income tax benefit, tax on foreign income			$ 19.9
Discrete income tax benefit, impact on effective tax rate (in basis points)			(3.20%)
Excess tax benefit from option exercises	$ 12.4	$ 12.9	$ 17.4	$ 19.7
Excess tax benefit, impact on effective tax rate (in basis points)	(3.80%)	(3.50%)	(2.80%)	(2.70%)