Income Taxes, Provision and Effective tax rate (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Taxes
Provision for income taxes	$ (91.8)	$ (100.0)	$ (250.0)	$ (280.8)
Effective tax rate (as a percent)	24.50%	23.80%	22.90%	24.30%
Excess tax benefit from option exercises	$ 1.6	$ 7.0	$ 21.3	$ 14.1
Excess tax benefit, impact on effective tax rate (in basis points)	(0.40%)	(1.70%)	(1.90%)	(1.20%)
Tender Offers [Member]
Income Taxes
Early extinguishment of debt, impact on effective tax rate (in basis points)	0.40%		0.10%