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Derivative Financial Instruments Gains and Losses (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended
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Mar. 31, 2013 | Mar. 31, 2012
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts |  |
Gain (Loss) on Hedging Activity | $ 99 | $ 1,652
Cash settlement (gain) and loss | (11,792) | (5,436)
Unrealized Gain (Loss) on Derivatives | 42,364 | 7,652
Unrealized and Realized Derivative loss | 30,572 | 2,216
Amount of (gain) loss reclassified from AOCL to realized hedge gain (loss) | 61 | (1,034)
Crude oil |  |
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts |  |
Cash settlement (gain) and loss | 277 | 8,299
Unrealized Gain (Loss) on Derivatives | 3,789 | 29,491
Natural Gas |  |
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts |  |
Cash settlement (gain) and loss | (9,824) | (15,212)
Unrealized Gain (Loss) on Derivatives | 40,069 | (17,634)
Natural Gas Liquids |  |
Unrealized and realized gain and loss from derivative cash settlements and changes in fair value of derivative contracts |  |
Cash settlement (gain) and loss | (2,245) | 1,477
Unrealized Gain (Loss) on Derivatives | $ (1,494) | $ (4,205)

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- Definition Realized gain (loss) recognized in earnings from the settlement of derivative instruments not designated as hedges. + References No definition available. + Details
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- Definition Gain (loss) on derivative instruments not qualifying as hedges from changes in the fair value and realized gains (losses) on derivatives settled in cash + References No definition available. + Details
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- Definition Gain (loss) incurred in hedging activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959 + Details
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- Definition The amount of net gains or losses on price risk cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income. + References No definition available. + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -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 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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