Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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+ Details

- Definition

Net of tax effect change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges after taxes. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk. The change includes an entity's share of an equity investee's increase or decrease in deferred hedging gains or losses. While for technical reasons this element has no balance attribute, the default assumption is a credit balance consistent with its label.

+ References

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+ Details

- Definition

Pre tax reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk.

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+ Details

Derivative Instruments (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
Derivative Instruments (Details) (USD $)	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2012	Dec. 31, 2010
Discontinuance of cash flow hedge accounting
Unrealized losses, before tax due to a change in the fair value of open commodity and interest rate derivative contracts designated as cash flow hedges	$ 39,900,000	$ 39,900,000		$ 70,700,000
Unrealized losses, after tax due to a change in the fair value of open commodity and interest rate derivative contracts designated as cash flow hedges	(24,761,000)	(24,761,000)		(43,806,000)
Reclassified unrealized losses, before tax from AOCL into earnings	15,300,000	30,700,000
Reclassified unrealized losses, after tax from AOCL into earnings	9,500,000	19,045,000
Net losses after-tax expected to be reclassified into earnings from AOCL during the next twelve months			$ 21,500,000
Three-way collars \| February 2011 - December 2013 \| Oil Bbl/D \| Floor price $70 \| Ceiling price $116.50 \| Swap price $90.00
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	1,000	1,000
2011 \| Oil Bbl/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	20,020	20,020
2011 \| Natural Gas MMBtu/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	15,000	15,000
2012 \| Oil Bbl/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	19,000	19,000
2012 \| Natural Gas MMBtu/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	15,000	15,000
2013 \| Oil Bbl/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	13,000	13,000
2014 \| Oil Bbl/D
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	2,000	2,000
Full year 2012 and 2013 \| Oil Bbl/D \| Floor price $70 \| Ceiling price $120.00 \| Swap price $90.00
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	1,000	1,000
Full year 2012 and 2013 \| Oil Bbl/D \| Floor price $70 \| Ceiling price $120.10 \| Swap price $95.00
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	1,000	1,000
June 2011 - December 2014 \| Oil Bbl/D \| Floor price $77.95 \| Ceiling price $ 115.00 \| Swap price $ 105.00
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	1,000	1,000
Full year 2012, 2013, and 2014 \| Oil Bbl/D \| Floor price $80.00 \| Ceiling price $ 119.60 \| Swap price $ 107.00
Notional amount of derivative instruments
Notional amount of derivatives (Bbl/MMBtu)	1,000	1,000