Employee Benefits (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by Employer	$ 4.0
SERP [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by Employer	1.9
Estimated Future Employer Contributions in Current Fiscal Year	0.1
Medical Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions by Employer	0.2
Estimated Future Employer Contributions in Current Fiscal Year	0.1
Pinedale Divestiture [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Curtailment loss	$ 0.7