Supplemental Information on Natural Gas and Oil Exploration, Development and Production Activities (Unaudited) - Proved Developed and Undeveloped Reserves (Parenthetical) (Detail)	Dec. 31, 2010 Mcf
Reserve Quantities [Line Items]
Proved undeveloped reserves related to discontinued operations	408,710,000
Discontinued Operations
Reserve Quantities [Line Items]
Proved reserves related to discontinued operations	906,371,000

The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61831-109447

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-10.(a)(2))

-URI http://asc.fasb.org/extlink&oid=27015464&loc=d3e511914-122862

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 10

-Paragraph a

-Subparagraph 2

-Article 4

Name:	us-gaap_ProvedDevelopedAndUndevelopedReservesNet
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant