Components of Deferred Tax Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Net [Abstract]
Postretirement/post-employment benefits	$ 19.5	$ 23.1
Deferred compensation	91.7	192.4
Pension costs	27.6	36.6
Basis differences in fixed assets	(52.0)	(80.2)
Rent	27.5	41.7
Interest	45.8	58.9
Accruals and reserves	18.4	17.2
Allowance for doubtful accounts	10.2	13.3
Basis differences in intangible assets	(281.3)	(405.0)
Investments in equity securities	(3.3)	(6.3)
Tax loss/tax credit carry forwards	357.9	354.6
Prepaid expenses	(1.7)	(2.9)
Deferred revenue	(38.2)	(32.0)
Other	44.7	44.3
Total deferred tax assets, net	266.8	255.7
Valuation allowance	(243.3)	(255.6)	$ (275.1)	$ (332.2)
Net deferred tax assets	$ 23.5	$ 0.1