Goodwill and Identifiable Assets (Future Amortization Expense) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 232.9	$ 227.3
Finite-Lived Intangible Assets, Amortization Expense, Next Rolling Twelve Months	27.4
Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Two	43.9
Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Three	37.8
Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Four	29.7
Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Five	24.3
Finite-Lived Intangible Assets, Amortization Expense, Rolling after Year Five	$ 69.8