Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Assets Carried at Fair Value by Level) (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 26.7	$ 26.3	$ 33.5
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3.2	2.5
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	22.4	22.7
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	1.1	1.1
Fixed income bonds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	22.5	22.2
Fixed income bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.2	0.0
Fixed income bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	22.3	22.2
Fixed income bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3.0	2.5
Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3.0	2.5
Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.1	0.5
Pooled separate accounts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Pooled separate accounts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.1	0.5
Pooled separate accounts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Guaranteed deposit account
Defined Benefit Plan Disclosure [Line Items]
Pension assets	1.1	1.1
Guaranteed deposit account | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Guaranteed deposit account | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0.0	0.0
Guaranteed deposit account | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 1.1	$ 1.1