| **SCHEDULE II- VALUATION AND QUALIFYING ACCOUNTS - USD ($) $ in Thousands**                                                                                                                                                                                                                                                                                                                           | 12 Months Ended |
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| Allowance for Doubtful Accounts [Member]                                                                                                                                                                                                                                                                                                                                                              |                 |   |   |   |
| **Movement in Valuation Allowances and Reserves [Roll Forward]**                                                                                                                                                                                                                                                                                                                                      |                 |   |   |   |
| Beginning Balance, January 1                                                                                                                                                                                                                                                                                                                                                                          |                 | $ 486 | $ 896 | $ 718 |
| Charged to Cost and Expense                                                                                                                                                                                                                                                                                                                                                                           |                 | 1,700 | 78 | 322 |
| Deductions                                                                                                                                                                                                                                                                                                                                                                                            | [1]             | 177 | 488 | 144 |
| Ending Balance, December 31                                                                                                                                                                                                                                                                                                                                                                           |                 | 2,009 | 486 | 896 |
| Valuation Allowance for Unproved Natural Gas and Crude Oil Properties [Member]                                                                                                                                                                                                                                                                                                                        |                 |   |   |   |
| **Movement in Valuation Allowances and Reserves [Roll Forward]**                                                                                                                                                                                                                                                                                                                                      |                 |   |   |   |
| Beginning Balance, January 1                                                                                                                                                                                                                                                                                                                                                                          |                 | 9,293 | 5,142 | 5,690 |
| Charged to Cost and Expense                                                                                                                                                                                                                                                                                                                                                                           |                 | 7,012 | 4,465 | 3,038 |
| Deductions                                                                                                                                                                                                                                                                                                                                                                                            | [1]             | 16,161 | 314 | 3,586 |
| Ending Balance, December 31                                                                                                                                                                                                                                                                                                                                                                           |                 | $ 144 | $ 9,293 | $ 5,142 |
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| [1]For allowance for doubtful accounts, deductions represent the write-off of accounts receivable deemed uncollectible. For valuation allowance for unproved crude oil and natural gas properties, deductions represent accumulated amortization of expired or abandoned unproved crude oil and natural gas properties, with a corresponding decrease to the historical cost of the associated asset. |

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| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, charged to costs and expenses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| - Definition
Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 09 -Article 12
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