Oil And Natural Gas Properties (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
Oil And Natural Gas Properties [Line Items]
Effects of cash flow hedges	$ 22.4
Discount rate used to calculate ceiling, percentage	10.00%
Jan'13 - Dec'13 [Member]
Oil And Natural Gas Properties [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, MMBoe	1.5
Apr'12 - Dec'12 [Member]
Oil And Natural Gas Properties [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, MMBoe	4.2

The quantity of future oil and gas production being hedged.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 12

-Section D

-Paragraph b

-Subsection 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 360

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 12.D.3(b))

-URI http://asc.fasb.org/extlink&oid=6601679&loc=d3e516453-122869

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant