Pension and Other Benefit Programs (Summary of Fair Value Of Assets Plan) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	$ 409.3	$ 386.1
Investments measured at net asset value	4.1	5.6
Net assets	413.4	391.7	$ 506.7
Collective trust funds - bonds
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	371.5	350.3
Collective trust funds - equities
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	34.3	32.6
Cash, Other Short-Term Investments and Payables, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	3.5	3.2
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	(0.3)	(0.3)
Level 1 [Member] | Collective trust funds - bonds
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	0.0	0.0
Level 1 [Member] | Collective trust funds - equities
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	0.0	0.0
Level 1 [Member] | Cash, Other Short-Term Investments and Payables, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	(0.3)	(0.3)
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	409.6	386.4
Level 2 [Member] | Collective trust funds - bonds
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	371.5	350.3
Level 2 [Member] | Collective trust funds - equities
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	34.3	32.6
Level 2 [Member] | Cash, Other Short-Term Investments and Payables, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	3.8	3.5
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	0.0	0.0
Level 3 [Member] | Collective trust funds - bonds
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	0.0	0.0
Level 3 [Member] | Collective trust funds - equities
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	0.0	0.0
Level 3 [Member] | Cash, Other Short-Term Investments and Payables, Net [Member]
Defined Benefit Plan Disclosure [Line Items]
Net assets measured at fair value	$ 0.0	$ 0.0