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Fair Value Measurements Proved and Unproved Oil and Gas Properties (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2015 USD ($) A | Sep. 30, 2014 USD ($) | Sep. 30, 2015 USD ($) A | Sep. 30, 2014 USD ($) | Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |
Discount Rate Used for Fair Value of Oil and Gas Properties | 12.00% |  |  | 12.00% |  |  |  |
Impairment of Oil and Gas Properties | $ 55,990,000 |  | $ 0 | $ 124,430,000 |  | $ 0 |  |
Proved Oil and Gas Property, Successful Effort Method | 7,468,331,000 |  |  | 7,468,331,000 |  |  | $ 7,348,436,000 |
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down |  |  |  | 98,600,000 |  |  |  |
Abandonment and impairment of unproved properties | 6,600,000 |  | $ 15,522,000 | 24,046,000 |  | $ 18,487,000 |  |
Unproved Oil and Gas Property, Successful Effort Method | 381,869,000 |  |  | 381,869,000 |  |  | 532,498,000 |
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |
Proved Oil and Gas Property, Successful Effort Method | 56,849,000 | [1] |  | 56,849,000 | [1] |  | 33,423,000 | [2]
Unproved Oil and Gas Property, Successful Effort Method | $ 0 |  |  | $ 0 |  |  | $ 0 |
Oil and Gas Properties [Member] |  |  |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |
Number of Periods Used for Price Assumptions of Strip Prices | A | 5 |  |  | 5 |  |  |  |
[1] | This represents a non-financial asset that is measured at fair value on a nonrecurring basis.
[2] | This represents a non-financial asset that is measured at fair value on a nonrecurring basis.

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- Definition Rate applied to the undiscounted amount of estimated cash flows from proved oil and gas properties to arrive at the present value recorded as of the balance sheet date. + References No definition available. + Details
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- Definition Represents the number of periods used for price assumptions of strip prices of assets or liabilities. + References No definition available. + Details
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- Definition Amount, before tax, of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a disposal group. Excludes discontinued operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2941-110230 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2443-110228 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 + Details
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- Definition The adjustment to reduce the value of existing agreements that specify the lessee's rights to use the leased property. This expense is charged when the estimates of future profits generated by the leased property are reduced. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2420-110228 + Details
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- Definition The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2921-110230 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 35 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28370743&loc=d3e66150-109466 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 + Details
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- Definition Oil and Gas properties with proved reserves under the successful effort method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Glossary Proved Properties -URI http://asc.fasb.org/extlink&oid=6522428 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 25 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=56951519&loc=d3e64746-109465 + Details
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- Definition Oil and Gas properties with unproved reserves under the successful effort method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=51678428&loc=d3e61926-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -Glossary Unproved Properties -URI http://asc.fasb.org/extlink&oid=6527831 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 25 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=56951519&loc=d3e64746-109465 + Details
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