Employee Benefits (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension curtailment loss				$ 11.2	$ 0.0
Funded Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension Contributions				2.0
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year				2.0
Unfunded Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension Contributions				2.9
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year				1.5
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension curtailment loss	[1]	$ 0.0	$ 0.0	0.0	0.4
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year				0.1
Other Postretirement Benefits Payments				0.4
Continuing Operations [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Postretirement Benefit Expense		$ 0.9	1.4	$ 14.1	8.2
Discontinued Operations [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other Postretirement Benefit Expense			$ 0.4		$ 1.4

[1] A curtailment is recognized immediately when there is a significant reduction in, or an elimination of, defined benefit accruals for current employees' future services. For the nine months ended September 30, 2015, these expenses are included on the Condensed Consolidated Statements of Operations within "General and administrative" expense as the expenses incurred in that period related to the Pension Plan amendment (see above). For the nine months ended September 30, 2014, these expenses are included within "Net gain (loss) from asset sales" as the expenses incurred in that period related to the Midcontinent property sales (see Note 3 – Acquisitions and Divestitures).