Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.0	$ 0.0	$ 0.0
Interest cost	1.1	0.7	0.7
Expected return of plan assets	(1.4)	(1.3)	(1.5)
Amortization of prior service credit	0.0	0.0	0.0
Amortization of net loss (gain)	0.5	0.4	0.4
Settlement	0.1	0.0	0.0
Net periodic benefit cost (credit)	0.3	(0.2)	(0.4)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.1	0.1
Interest cost	0.1	0.0	0.0
Expected return of plan assets	0.0	0.0	0.0
Amortization of prior service credit	0.0	0.0	(0.1)
Amortization of net loss (gain)	0.0	0.0	0.0
Settlement	0.0	0.0	0.0
Net periodic benefit cost (credit)	$ 0.2	$ 0.1	$ 0.0