Acquisitions & Divestitures Divestitures Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Midcontinent Divestitures [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from Sale of Property, Plant, and Equipment			$ 675.6
Gain (Loss) on Disposition of Oil and Gas and Timber Property	$ 4.6	$ (21.8)	(199.4)
Southern Region Divestitures [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from Sale of Property, Plant, and Equipment			101.3
Gain (Loss) on Disposition of Oil and Gas and Timber Property	$ 8.8	$ 5.9	$ 53.3