Operating Leases (Components of lease expense and Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease cost	$ 91.6	$ 70.0
Variable lease cost	23.4	26.8
Less: sublease income	(2.1)	(0.6)	$ (0.4)
Total lease expense	112.9	96.2
Operating cash flows from operating leases included in the measurement of lease liabilities	98.3	72.8
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 36.7	$ 167.7
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets