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Property And Equipment (Narrative) (Details) (USD $) | 3 Months Ended | 12 Months Ended | 23 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |  |
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Mar. 31, 2013 | Mar. 31, 2012 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2012 | Mar. 31, 2013 Diamondback [Member] member_of_board_of_directors advisor | Dec. 31, 2012 Diamondback [Member] advisor member_of_board_of_directors | 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] | Jan. 31, 2013 Diamondback [Member] Subsequent Event [Member] Accounts Receivable - Related Party [Member] | Mar. 31, 2013 Minimum [Member] | Dec. 31, 2012 Minimum [Member] | Mar. 31, 2013 Maximum [Member] | Dec. 31, 2012 Maximum [Member] | Mar. 31, 2013 Colorado [Member] | Dec. 31, 2012 Colorado [Member] | Mar. 31, 2013 Bakken [Member] | Dec. 31, 2012 Bakken [Member] | Mar. 31, 2013 Southern Louisiana [Member] | Dec. 31, 2012 Southern Louisiana [Member] | Mar. 31, 2013 Ohio [Member] | Dec. 31, 2012 Ohio [Member] | Mar. 31, 2013 Other [Member] | Dec. 31, 2012 Other [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 |  | $ 32,562,000 | $ 23,494,000 |  | $ 32,562,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capitalized general and administrative costs | 2,900,000 | 2,000,000 | 9,068,000 | 5,368,000 | 4,117,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capitalized costs of oil and natural gas properties excluded from amortization | 869,879,000 | 626,295,000 | 626,295,000 | 138,623,000 |  | 626,295,000 |  |  |  |  |  |  |  |  |  |  |  |  | 6,088,000 | 5,998,000 | 301,000 | 295,000 | 789,000 | 774,000 | 862,655,000 | 619,182,000 | 46,000 | 46,000
Loss on disposal of Belize properties, net of tax |  |  | 3,465,000 | 0 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected number of years amortization will commence |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years | 3 years | 5 years | 5 years |  |  |  |  |  |  |  |  |  |
Investment (shares) |  |  |  |  |  |  |  |  |  |  | 7,914,036 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Promissory note receivable |  |  |  |  |  |  |  |  |  |  | 63,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment received from Diamondback | (3,592,000) | 1,718,000 | (2,404,000) | 13,067,000 | 5,460,000 |  |  |  |  |  |  |  | 18,600,000 | 18,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on sale of oil and gas property | (427,000) | 0 | 7,300,000 | 0 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Oil and Gas property, decrease related to contribution |  |  |  |  |  | $ 213,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership requirement to meet agreement |  |  |  |  |  |  | 10.00% | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of directors allowed to serve on Board |  |  |  |  |  |  | 1 | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of advisors allowed to serve on Board |  |  |  |  |  |  | 1 | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  |  |  |  |  | 21.40% | 22.50% |  | 35.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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