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Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
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12 Months Ended | |||||
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Dec. 31, 2012
purchaser
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Mar. 31, 2013
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Mar. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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| Summary Of Significant Accounting Policies [Line Items] | ||||||
| Number Of Purchasers | 2 | |||||
| Accounts receivable, collection period | 30 days | |||||
| Conversion ratio, gas to barrels of oil | 6 | |||||
| Capitalized costs of oil and natural gas properties excluded from amortization | $ 626,295,000 | $ 869,879,000 | $ 626,295,000 | $ 138,623,000 | ||
| Gas balancing payable | 354,000 | 0 | ||||
| Cumulative transaltion adjustment | $ 2,442,000 | $ 1,087,000 | $ 2,952,000 | $ 696,000 | ||
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Minimum [Member]
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| Summary Of Significant Accounting Policies [Line Items] | ||||||
| Useful life | 3 years | |||||
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Maximum [Member]
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| Summary Of Significant Accounting Policies [Line Items] | ||||||
| Useful life | 30 years |
| X | ||||||||||
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- Definition
Accounts Receivable, Collection Period No definition available.
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| X | ||||||||||
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- Definition
Conversion Ratio, Gas To Barrels Of Oil No definition available.
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| X | ||||||||||
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- Definition
Number Of Purchasers No definition available.
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| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The sum of the capitalized costs incurred, as of the balance sheet date, of unproved properties excluded from amortization including acquisition costs, exploration costs, development costs, and production costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Carrying value as of the balance sheet date of obligations incurred and payable to an underproduced working interest owner when an overproduced working interest owner has sold gas in excess of the party's ownership percentage. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. No definition available.
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