Supplemental Information on Oil and Natural Gas Operations - Unaudited - Summary of Estimated Proved Oil and Natural Gas Reserve (Detail) MMcf in Thousands, MBbls in Thousands	12 Months Ended
Dec. 31, 2015 MBbls MMcf	Dec. 31, 2014 MBbls MMcf	Dec. 31, 2013 MBbls MMcf
Oil (MBbls) [Member]
Proved Developed and Undeveloped Reserves [Abstract]
Estimated proved reserves, beginning balance \| MBbls	42,397	43,827	44,918
Revisions of previous estimates \| MBbls	(6,818)	(624)	3,606
Extensions, discoveries and other additions \| MBbls	862	9,650	2,367
Purchase of producing properties \| MBbls	685
Sale of reserves \| MBbls	(859)	(4,888)	(170)
Production \| MBbls	(5,991)	(5,568)	(6,894)
Estimated proved reserves, ending balance \| MBbls	30,276	42,397	43,827
Estimated proved developed reserves \| MBbls	21,734	22,957	27,920
Estimated proved undeveloped reserves \| MBbls	8,542	19,440	15,907
Natural Gas Liquids (MBbls) [Member]
Proved Developed and Undeveloped Reserves [Abstract]
Estimated proved reserves, beginning balance \| MBbls	27,817	23,297	18,066
Revisions of previous estimates \| MBbls	(20,777)	(331)	2,439
Extensions, discoveries and other additions \| MBbls	11	7,521	4,395
Purchase of producing properties \| MBbls	1,808
Sale of reserves \| MBbls	0	(556)	0
Production \| MBbls	(2,401)	(2,114)	(1,603)
Estimated proved reserves, ending balance \| MBbls	6,458	27,817	23,297
Estimated proved developed reserves \| MBbls	4,784	13,743	11,569
Estimated proved undeveloped reserves \| MBbls	1,674	14,074	11,728
Natural Gas (MMcfe) [Member]
Proved Developed and Undeveloped Reserves [Abstract]
Estimated proved reserves, beginning balance \| MMcf	493,843	460,766	395,374
Revisions of previous estimates \| MMcf	(362,102)	(4,631)	36,006
Extensions, discoveries and other additions \| MMcf	1,499	131,617	79,729
Purchase of producing properties \| MMcf	26,136
Sale of reserves \| MMcf	(1,061)	(46,483)	(214)
Production \| MMcf	(36,457)	(47,426)	(50,129)
Estimated proved reserves, ending balance \| MMcf	121,858	493,843	460,766
Estimated proved developed reserves \| MMcf	90,262	249,924	246,946
Estimated proved undeveloped reserves \| MMcf	31,596	243,919	213,820
Oil And Natural Gas (MMcfe) [Member]
Proved Developed and Undeveloped Reserves [Abstract]
Estimated proved reserves, beginning balance \| MMcf	915,124	863,513	773,285
Revisions of previous estimates \| MMcf	(527,675)	(10,362)	72,275
Extensions, discoveries and other additions \| MMcf	6,738	234,639	120,299
Purchase of producing properties \| MMcf	41,095
Sale of reserves \| MMcf	(6,213)	(79,151)	(1,235)
Production \| MMcf	(86,809)	(93,515)	(101,111)
Estimated proved reserves, ending balance \| MMcf	342,260	915,124	863,513
Estimated proved developed reserves \| MMcf	249,366	470,118	483,885
Estimated proved undeveloped reserves \| MMcf	92,894	445,006	379,628

Proved Developed and Undeveloped Reserves, Extensions, Purchase Of Production Properties

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61831-109447

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- Definition

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.

+ References

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

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- Definition

Production of proved reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61831-109447

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- Definition

Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61831-109447

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- Definition

Sales of minerals in place.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61831-109447

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- Definition

Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61884-109447

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61797-109447

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- Definition

Net quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other renewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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