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Derivative Instruments (Schedule of Outstanding Commodity Derivative Instruments) (Detail) (USD $) In Thousands, unless otherwise specified | 9 Months Ended
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Sep. 30, 2012 bbl
Derivative Instruments [Line Items] |
Fair Value Asset (Liability) | $ 25,734
2012 Two-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 819,000
Average Floor Price | 88.61
Average Ceiling Price | 105.59
Fair Value Asset (Liability) | 975
Settlement Period | 2012
2012 Three-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 910,000
Average Sub-Floor Price | 66.25
Average Floor Price | 90.25
Average Ceiling Price | 110.04
Fair Value Asset (Liability) | 841
Settlement Period | 2012
Two Thousand Twelve Swap Contracts [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 91,000
Average Swap Price | 94.61
Fair Value Asset (Liability) | 130
Settlement Period | 2012
2013 Two-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 1,782,000
Average Floor Price | 86.50
Average Ceiling Price | 98.93
Fair Value Asset (Liability) | (1,164)
Settlement Period | 2013
2013 Three-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 2,023,420
Average Sub-Floor Price | 65.30
Average Floor Price | 92.51
Average Ceiling Price | 112.63
Fair Value Asset (Liability) | 8,561
Settlement Period | 2013
2013 Put Spreads [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 1,717,080
Average Sub-Floor Price | 70.71
Average Floor Price | 91.24
Fair Value Asset (Liability) | 9,931
Settlement Period | 2013
Two Thousand Thirteen Swap Contracts [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 699,000
Average Swap Price | 96.41
Fair Value Asset (Liability) | 1,850
Settlement Period | 2013
2014 Two-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 139,500
Average Floor Price | 86.11
Average Ceiling Price | 97.69
Fair Value Asset (Liability) | (84)
Settlement Period | 2014
2014 Three-Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 1,495,030
Average Sub-Floor Price | 70.60
Average Floor Price | 91.43
Average Ceiling Price | 110.30
Fair Value Asset (Liability) | 3,229
Settlement Period | 2014
2014 Put Spreads [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 150,970
Average Sub-Floor Price | 71.03
Average Floor Price | 91.03
Fair Value Asset (Liability) | 1,019
Settlement Period | 2014
Two Thousand Fourteen Swap Contracts [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 62,000
Average Swap Price | 96.49
Fair Value Asset (Liability) | 215
Settlement Period | 2014
2015 Three Way Collars [Member] |
Derivative Instruments [Line Items] |
Total Notional Amount of Oil (Barrels) | 124,000
Average Sub-Floor Price | 71.25
Average Floor Price | 91.25
Average Ceiling Price | 109.96
Fair Value Asset (Liability) | $ 231
Settlement Period | 2015

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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition The average strike price of the sold put that establishes the price at which if the market price falls below, the minimum price would be index price plus the difference between the purchased put (floor) and the sold put strike price. + References No definition available. + Details
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- Details
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- Definition Derivatives, Maturity Date + References No definition available. + Details
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- Definition The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract. + References No definition available. + Details
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- Definition The average floor rate on a group of price risk derivatives such as floors or collars. A payment or receipt is triggered if the market rate falls below the floor rate on the contract. + References No definition available. + Details
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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13495-108611 + Details
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- Definition Average fixed price related to the group of price risk swap derivatives. + References No definition available. + Details
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