Income Taxes, 2017 Tax Cuts and Jobs Act (Details) $ in Millions			3 Months Ended		12 Months Ended
	Dec. 31, 2017 item	Dec. 22, 2017	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
U.S. statutory federal tax rate (as a percent)		35.00%			21.00%	35.00%	35.00%
Estimated Tax Act Charge				$ 398.5
Estimated Transition Tax				259.4
Provisional charge on unremitted foreign earnings				176.6
Income tax expense (benefit) associated with the remeasurement of net deferred tax liabilities				$ (37.5)
Number of components | item	3
Income tax benefit			$ 14.5		$ 14.5
Period for payment of Transition Tax					8 years