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Property And Equipment (Narrative) (Details) (USD $) | 3 Months Ended |  | 3 Months Ended |  |  |  |  | 1 Months Ended | 3 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2013 | Mar. 31, 2012 | Dec. 31, 2012 | Mar. 31, 2013 Diamondback [Member] member_of_board_of_directors advisor | Oct. 23, 2012 Diamondback [Member] | Oct. 17, 2012 Diamondback [Member] | Oct. 11, 2012 Diamondback [Member] | May 07, 2012 Diamondback [Member] | Jan. 31, 2013 Diamondback [Member] Accounts Receivable - Related Party [Member] | Mar. 31, 2013 Minimum [Member] | Mar. 31, 2013 Maximum [Member]
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool | $ 35,500,000 |  |  |  |  |  |  |  |  |  |
Capitalized general and administrative costs | 2,900,000 | 2,000,000 |  |  |  |  |  |  |  |  |
Capitalized costs of oil and natural gas properties excluded from amortization | 869,879,000 | 626,295,000 | 626,300,000 |  |  |  |  |  |  |  |
Expected number of years amortization will commence |  |  |  |  |  |  |  |  |  | 3 years | 5 years
Investment (shares) |  |  |  |  |  |  | 7,914,036 |  |  |  |
Promissory note receivable |  |  |  |  |  |  | 63,600,000 |  |  |  |
Payment received from Diamondback | $ (3,592,000) | $ 1,718,000 |  |  |  |  |  |  | $ 18,600,000 |  |
Ownership requirement to meet agreement |  |  |  | 10.00% |  |  |  |  |  |  |
Number of directors allowed to serve on Board |  |  |  | 1 |  |  |  |  |  |  |
Number of advisors allowed to serve on Board |  |  |  | 1 |  |  |  |  |  |  |
Ownership interest |  |  |  |  | 21.40% | 22.50% |  | 35.00% |  |  |

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