Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Taxes [Line Items]
Unrecognized tax benefits	$ 227.0		$ 226.4
Decrease of income tax provision	43.9
Interest included in unrecognized tax benefits	58.0		57.4
Tax benefit from repatriation of foreign earnings		$ 31.9
Income tax expense related to Tax Cuts and Jobs Act Of 2017	2.6
Jefferies
Income Taxes [Line Items]
Unrecognized tax benefits	$ 173.4		$ 177.8