Acquisitions & Divestitures (Schedule Of Purchase Accounting Entries) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014
Significant Acquisitions and Disposals [Line Items]
Payments to Acquire Businesses, Gross		$ 945.0
Business Combination Consideration Receivable		2.9
Payments to Acquire Businesses Net		942.1
Liabilities incurred		(13.2)
Fair value of assets acquired (liabilities assumed)	942.1	942.1
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)	480.9	480.9
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	942.1
Liabilities incurred		$ (9.7)