Discontinued Operations (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Value of midstream business sold					$ 2,500.0
Debt Refinanced In Business Sale					230.0
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax					1,800.0
Discontinued Operation, Amount of Continuing Cash Flows after Disposal	$ 24.9	$ 31.4	$ 94.2	$ 105.4
Depreciation, depletion and amortization	$ 238.1	251.4	$ 649.3	712.5
Employee Retention Bonus Cost					$ 10.4
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) Attributable to Parent		7.9		20.4
Depreciation, depletion and amortization		14.3		43.1
Payments to Acquire Oil and Gas Property and Equipment				45.6
Employee Retention Bonus Cost		$ 2.3		$ 7.1