Pensions and Postretirement Benefits (Summary of Pension Plan Asset Allocation By Level) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	$ 134.8	$ 120.2
Common stock
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	41.8	40.0
Equity securities
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	39.8	29.0
Foreign stock
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	7.3	5.4
U.S. Government obligations
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	5.8	8.1
Fixed income securities
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	13.7	14.1
Corporate bonds
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	10.2	6.3
Cash and cash equivalents
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	1.4	3.3
Common collective trusts
Schedule of pension plans assets by level within the fair value hierarchy
Investments measured at net asset value	0.7	1.1
Hedge funds
Schedule of pension plans assets by level within the fair value hierarchy
Investments measured at net asset value	14.1	12.9
Level 1
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	120.0	106.2
Level 1 | Common stock
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	41.8	40.0
Level 1 | Equity securities
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	39.8	29.0
Level 1 | Foreign stock
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	7.3	5.4
Level 1 | U.S. Government obligations
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	5.8	8.1
Level 1 | Fixed income securities
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	13.7	14.1
Level 1 | Corporate bonds
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	10.2	6.3
Level 1 | Cash and cash equivalents
Schedule of pension plans assets by level within the fair value hierarchy
Fair value of pension plan assets	$ 1.4	$ 3.3