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Supplemental Oil and Natural Gas Reserve Data (unaudited) (Proved Developed and Undeveloped Reserves) (Details)
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12 Months Ended | 12 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Dec. 31, 2013
Boe
|
Dec. 31, 2012
Boe
|
Dec. 31, 2011
Boe
|
Dec. 31, 2010
Boe
|
Dec. 31, 2013
Crude Oil [Member]
bbl
|
Dec. 31, 2012
Crude Oil [Member]
bbl
|
Dec. 31, 2011
Crude Oil [Member]
bbl
|
Dec. 31, 2009
Crude Oil [Member]
bbl
|
Dec. 31, 2013
Natural Gas [Member]
ft3
|
Dec. 31, 2012
Natural Gas [Member]
ft3
|
Dec. 31, 2011
Natural Gas [Member]
ft3
|
Dec. 31, 2009
Natural Gas [Member]
ft3
|
|
| Proved developed and undeveloped reserves: | ||||||||||||
| Beginning of period | 10,780,000 | 10,075,000 | 8,149,000 | 19,753,000,000 | 35,118,000,000 | 32,957,000,000 | ||||||
| Revisions to previous estimates | (2,540,000) | (488,000) | (110,000) | (5,351,000,000) | (10,838,000,000) | 486,000,000 | ||||||
| Purchase of reserves in place | 150,000 | 38,000 | 0 | 317,000,000 | 115,000,000 | 0 | ||||||
| Sale of reserves in place | (3,294,000) | (504,000) | (30,000) | (4,576,000,000) | (4,404,000,000) | (308,000,000) | ||||||
| Extensions and discoveries | 7,713,000 | 2,636,000 | 3,062,000 | 10,619,000,000 | 3,350,000,000 | 7,064,000,000 | ||||||
| Production | (911,000) | (977,000) | (996,000) | (3,011,000,000) | (3,588,000,000) | (5,081,000,000) | ||||||
| End of period | 11,898,000 | 10,780,000 | 10,075,000 | 8,149,000 | 17,751,000,000 | 19,753,000,000 | 35,118,000,000 | 32,957,000,000 | ||||
| Beginning of period | 4,955,000 | 5,069,000 | 4,503,000 | 10,680,000,000 | 11,605,000,000 | 12,715,000,000 | ||||||
| End of period | 5,960,000 | 4,955,000 | 5,069,000 | 9,059,000,000 | 10,680,000,000 | 11,605,000,000 | ||||||
| Beginning of period | 7,470,000 | 6,735,000 | 7,003,000 | 6,622,000 | ||||||||
| End of period | 7,470,000 | 6,735,000 | 7,003,000 | 6,622,000 | ||||||||
| Beginning of period | 5,825,000 | 5,006,000 | 3,645,000 | 9,073,000,000 | 23,513,000,000 | 20,241,000,000 | ||||||
| End of period | 5,938,000 | 5,825,000 | 5,006,000 | 8,692,000,000 | 9,073,000,000 | 23,513,000,000 | ||||||
| Beginning of period | 7,387,000 | 7,337,000 | 8,925,000 | 7,019,000 | ||||||||
| End of period | 7,387,000 | 7,337,000 | 8,925,000 | 7,019,000 | ||||||||