Financing (Components Of Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Apr. 04, 2023	Dec. 31, 2022	Feb. 05, 2018	Dec. 31, 2013	Nov. 30, 2006
Debt Instrument [Line Items]
Total short-term borrowings	$ 4.6		$ 299.7
Other deferred financing costs associated with credit facilities	(3.4)		0.0
Total long-term debt	640.3		545.1
Debt discounts and debt issuance costs	10.1		$ 5.6
4.45% notes due December 2023 | Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate		4.45%	4.45%		4.45%
Total short-term borrowings	$ 0.0		$ 299.7
6.55% notes due November 2036 | Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	6.55%		6.55%			6.55%
Long-term debt	$ 198.6		$ 198.6
4.20% notes due March 2048 | Senior Notes
Debt Instrument [Line Items]
Debt instrument, interest rate	4.20%		4.20%	4.20%
Long-term debt	$ 346.6		$ 346.5
Term Facility | Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Long-term debt	98.5		0.0
Term Facility | Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Total short-term borrowings	$ 4.6		$ 0.0