Fair Value Measurements (Financial Assets And Liabilities Carried At Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets:
Available-for-sale securities	$ 45.4	$ 170.1
Liabilities:
Deferred compensation plans	62.9	52.2
Quoted Prices in Active Market (Level 1)
Assets:
Available-for-sale securities	0.0	117.8
Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	45.4	52.3
Liabilities:
Deferred compensation plans	62.9	52.2
Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities	0.0	0.0
Liabilities:
Deferred compensation plans	$ 0.0	$ 0.0