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Supplemental Oil and Gas Reserve Information - Net Proved, Proved Developed and Proved Undeveloped Reserves (Detail) | 12 Months Ended
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Dec. 31, 2013 MBbls MBoe MMcf | Dec. 31, 2013 MMcf MBoe MBbls | Dec. 31, 2012 MMcf MBbls MBoe | Dec. 31, 2012 MBbls MBoe MMcf | Dec. 31, 2011 MMcf MBbls MBoe | Dec. 31, 2011 MBbls MBoe MMcf
Estimated Net Proved, Proved Developed and Proved Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Proved reserves (Volume), beginning balance | 128,090 | 128,090 | 57,900 | 57,900 | 19,379 | 19,379
Proved reserves (Energy), beginning balance | 143,345 | 143,345 | 78,715 | 78,715 | 39,780 | 39,780
Revisions of previous estimates (Volume) | (3,390) | (10,411) | (8,495) | (567) | (159) | (262)
Revisions of previous estimates (Energy) | (5,125) | (5,125) | (1,983) | (1,983) | (288) | (288)
Extensions, discoveries and other additions (Volume) | 40,784 | 31,856 | 45,759 | 66,245 | 40,220 | 36,464
Extensions, discoveries and other additions (Energy) | 46,094 | 46,094 | 73,871 | 73,871 | 43,168 | 43,168
Sales of reserves in place (Volume) |  |  | 0 | 0 | (518) | (56)
Sales of reserves in place (Energy) |  |  | 0 | 0 | (142) | (142)
Purchases of reserves in place (Volume) | 37,459 | 49,631 | 512 | 881 | 65 | 100
Purchases of reserves in place (Energy) | 45,731 | 45,731 | 966 | 966 | 111 | 111
Production (Volume) | (11,133) | (7,450) | (4,146) | (7,533) | (1,087) | (3,732)
Production (Energy) | (12,375) | (12,375) | (8,224) | (8,224) | (3,914) | (3,914)
Net proved reserves (Volume), closing balance | 175,979 | 175,979 | 128,090 | 128,090 | 57,900 | 57,900
Net proved reserves (Energy), closing balance | 227,920 | 227,920 | 143,345 | 143,345 | 78,715 | 78,715
Proved developed reserves (Volume) | 92,170 | 92,170 | 62,602 | 62,602 | 24,535 | 24,535
Proved developed reserves (Energy) | 122,136 | 122,136 | 70,051 | 70,051 | 35,839 | 35,839
Proved undeveloped reserve (Volume) | 83,809 | 83,809 | 65,488 | 65,488 | 33,365 | 33,365
Proved undeveloped reserves (Energy) | 105,784 | 105,784 | 73,294 | 73,294 | 42,876 | 42,876

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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 + Details
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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 + Details
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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 + Details
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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 + Details
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- Definition Energy measure of interests in proved developed reserves of 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. + References No definition available. + Details
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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 4 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61797-109447 Reference 2: 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 + Details
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