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Property And Equipment (Narrative) (Details) (USD $)
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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
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Mar. 31, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2012
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Mar. 31, 2013
Diamondback [Member]
member_of_board_of_directors
advisor
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Dec. 31, 2012
Diamondback [Member]
advisor
member_of_board_of_directors
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Oct. 23, 2012
Diamondback [Member]
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Oct. 17, 2012
Diamondback [Member]
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Oct. 11, 2012
Diamondback [Member]
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May 07, 2012
Diamondback [Member]
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Jan. 31, 2013
Diamondback [Member]
Accounts Receivable - Related Party [Member]
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Jan. 31, 2013
Diamondback [Member]
Subsequent Event [Member]
Accounts Receivable - Related Party [Member]
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Mar. 31, 2013
Minimum [Member]
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Dec. 31, 2012
Minimum [Member]
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Mar. 31, 2013
Maximum [Member]
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Dec. 31, 2012
Maximum [Member]
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Mar. 31, 2013
Colorado [Member]
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Dec. 31, 2012
Colorado [Member]
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Mar. 31, 2013
Bakken [Member]
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Dec. 31, 2012
Bakken [Member]
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Mar. 31, 2013
Southern Louisiana [Member]
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Dec. 31, 2012
Southern Louisiana [Member]
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Mar. 31, 2013
Ohio [Member]
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Dec. 31, 2012
Ohio [Member]
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Mar. 31, 2013
Other [Member]
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Dec. 31, 2012
Other [Member]
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| 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% | |||||||||||||||||||||||||