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Supplemental Financial Information Exploration and Production (Details) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
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Capitalized Costs Relating to Oil and Gas Producing Activities, by Geographic Area [Line Items] |  |  |
Capitalized costs, oil and gas producing activities, subject to amortization | $ 2,345,114 | $ 2,138,565 | $ 1,815,380
Capitalized Costs of Unproved Properties Excluded from Amortization, Cumulative | 232,462 | 182,402 | 178,214
Capitalized Costs, Oil and Gas Producing Activities, Gross | 2,577,576 | 2,320,967 | 1,993,594
Capitalized Costs, Accumulated Depreciation, Depletion, Amortization and Valuation Allowance Relating to Oil and Gas Producing Activities | 1,229,654 | 1,093,723 | 969,630
Capitalized Costs, Oil and Gas Producing Activities, Net | $ 1,347,922 | $ 1,227,244 | $ 1,023,964

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- Definition Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59M -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6821537&loc=d3e61901-109447 + Details
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- Definition The sum of capitalized costs relating to oil and gas producing activities before accounting for accumulated depreciation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59M -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6821537&loc=d3e61901-109447 + Details
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