Acquisitions & Divestitures (Schedule Of Purchase Accounting Entries) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Significant Acquisitions and Disposals [Line Items]
Payments to Acquire Businesses Net		$ 941.8
Liabilities incurred		(15.5)	[1]
Fair value of assets acquired (liabilities assumed)	941.8	941.8
Proved Property [Member]
Significant Acquisitions and Disposals [Line Items]
Fair value of assets acquired (liabilities assumed)	472.1	472.1
Unproved Property [Member]
Significant Acquisitions and Disposals [Line Items]
Fair value of assets acquired (liabilities assumed)	480.6	480.6
Other Liabilities [Member]
Significant Acquisitions and Disposals [Line Items]
Fair value of assets acquired (liabilities assumed)	(1.2)	(1.2)
Permian Basin [Member]
Significant Acquisitions and Disposals [Line Items]
Payments to Acquire Businesses, Gross	941.8
Liabilities incurred		$ (9.7)

[1] Additions include $9.7 million related to the Permian Basin Acquisition (see Note 3 - Acquisitions and Divestitures).