Employee Benefits (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	$ 128.7	$ 124.5
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Employer	4.0
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	4.0
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.4
Defined Benefit Plan, Curtailment loss			$ 11.2
Pension Plan [Member] | Active Employees [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Number of Employees Covered	30
Defined Benefit Plan, Percentage Of Employees Covered	5.00%
Pension Plan [Member] | Non-active Employees [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Number of Employees Covered	184
Pension Plan and SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 6.0	7.2
Defined Benefit Plan, Curtailment loss	0.7	0.0	11.2
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year	$ 1.9
Medical Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Number of Eligible	17
Defined Benefit Plan, Contributions by Employer	$ 0.1	0.4
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	0.3
Defined Benefit Plan, Curtailment loss	0.0	$ 0.0	$ 0.0
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year	(0.3)
SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Contributions by Employer	2.0
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	0.7
Defined Benefit Plan, Curtailment loss	$ 0.7