Pensions and Postretirement Benefits (Summary of Pension Plan Asset Allocation By Level) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 161.3	$ 144.4
Common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	30.7	40.0
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	63.1	43.9
Foreign stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	6.8	7.0
U.S. Government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	8.5	8.6
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	6.4	11.5
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	16.0	14.2
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	5.9	2.7
Common collective trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	3.2	0.0
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	20.7	16.5
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	137.4	127.9
Level 1 | Common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	30.7	40.0
Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	63.1	43.9
Level 1 | Foreign stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	6.8	7.0
Level 1 | U.S. Government obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	8.5	8.6
Level 1 | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	6.4	11.5
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	16.0	14.2
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension plan assets	$ 5.9	$ 2.7