Acquisitions and Divestitures Divestitures (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2014	Sep. 30, 2013
Midcontinent Divestitures [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from Sale of Property, Plant, and Equipment	$ 692.9
Gain (Loss) on Disposition of Oil and Gas and Timber Property	(199.4)
Northern Region Divestitures [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from Sale of Property, Plant, and Equipment		138.5
Gain (Loss) on Disposition of Oil and Gas and Timber Property		96.2
Southern Region Divestitures [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from Sale of Property, Plant, and Equipment			94.9	67.3
Gain (Loss) on Disposition of Oil and Gas and Timber Property			$ 53.3	$ 9.5