Income Taxes (Schedule of Components Of Income Tax Expense Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Provisions for Income Taxes Recorded in the Consolidated Statements of Income [Abstract]
U.S. Federal, current expense	$ 38.5	$ 41.9	$ 20.5
State, current expense	11.4	12.4	6.9
Foreign, current expense	4.5	4.4	4.6
Total current expense	54.4	58.7	32.0
U.S. Federal, deferred expense	(7.8)	(3.0)	2.5
State, deferred expense	(2.3)	(0.8)	0.8
Foreign, deferred expense	(0.1)	0.1	0.1
Total deferred (benefit) expense	(10.2)	(3.7)	3.4
Total income tax provision	$ 44.2	$ 55.0	$ 35.4