Benefit Plans, Fair Values by Asset Category (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Weighted average asset allocations value [Abstract]
Fair value of plan assets	$ 296.7	$ 320.2
Equity Securities [Member]
Weighted average asset allocations value [Abstract]
Fair value of plan assets	162.8	179.2
Fixed Income Securities [Member]
Weighted average asset allocations value [Abstract]
Fair value of plan assets	113.6	116.0
Real Estate [Member]
Weighted average asset allocations value [Abstract]
Fair value of plan assets	2.3	2.4
Other [Member]
Weighted average asset allocations value [Abstract]
Fair value of plan assets	$ 18.0	$ 22.6