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Accounts Receivable-Related Party (Details) (USD $) In Thousands, unless otherwise specified |  |  | 3 Months Ended | 12 Months Ended |  | 3 Months Ended | 6 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2012 | Dec. 31, 2011 | Mar. 13, 2012 Charles E. Davidson [Member] | Dec. 31, 2011 Charles E. Davidson [Member] | Mar. 01, 2008 Charles E. Davidson [Member] | Jun. 30, 2012 Everest Operations Management LLC [Member] | Jun. 30, 2011 Everest Operations Management LLC [Member] | Jun. 30, 2012 Everest Operations Management LLC [Member] | Jun. 30, 2011 Everest Operations Management LLC [Member] | Jun. 30, 2012 Windsor Niobrara LLC [Member]
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |  |  |
Affiliates Participation Percentage in Acquisition of Leases |  |  |  |  |  |  |  |  |  | 50.00%
Accounts receivable-related parties | $ 27,182 | $ 4,731 |  |  |  |  |  |  |  |
Reimbursement for general and administrative expenses performed for related party under acquisition team agreement |  |  |  |  |  | $ 208 | $ 401 | $ 533 | $ 401 |
Common stock ownership percentage by an individual |  |  | 9.50% | 13.30% |  |  |  |  |  |
Percentage of Proportionate Share of the Acquisition or Divestiture Consideration Payable to Affiliates |  |  |  |  |  | 1.00% |  | 1.00% |  |
Cancellation of Agreement Required Written Notice Term |  |  |  |  | 60 days |  |  |  |  |
Cancellation of Agreement Required Wrriten Notice Term, Counterparty |  |  |  |  | 30 days |  |  |  |  |
Breech of Contract, Cure Period |  |  |  |  | 30 days |  |  |  |  |

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