Derivative Activities (Details 4) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Effects of cash flow hedges and other hedges on accumulated other comprehensive income (loss)
Change in unrealized deferred hedging gains, Tax Effect	$ (10,454)	$ 2,611	$ (7,414)	$ (29,618)
Realized Gain Reclassified from AOCI into Revenue, Income taxes	(9,107)	(6,969)	(23,441)	(7,431)
Change in Hedge Derivative Fair Value, effects of cash flow hedges on accumulated other comprehensive income (loss), total	17,424	(4,257)	17,537	48,325
Realized Gain Reclassified from AOCI into Revenue, effects of cash flow hedges on accumulated other comprehensive income (loss), total	15,178	11,371	39,068	12,124
Collars [Member]
Effects of cash flow hedges and other hedges on accumulated other comprehensive income (loss)
Change in Hedge Derivative Fair Value	23,223	(6,887)	22,424	77,930
Realized Gain Reclassified from AOCI into Revenue	24,285	18,340	53,902	19,555
Swap [Member]
Effects of cash flow hedges and other hedges on accumulated other comprehensive income (loss)
Change in Hedge Derivative Fair Value	4,655	0	2,115	0
Realized Gain Reclassified from AOCI into Revenue	0	0	0	0
Collars discontinued operations [Member]
Effects of cash flow hedges and other hedges on accumulated other comprehensive income (loss)
Change in Hedge Derivative Fair Value	0	19	412	13
Realized Gain Reclassified from AOCI into Revenue	$ 0	$ 0	$ 8,607	$ 0

Pre tax change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges, net of reclassifications into earnings 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. 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.

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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+ Details

- Definition

Total tax effect of the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. 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+ Details

- Definition

Pre tax change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges. 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. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

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+ Details

- Definition

Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

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+ Details

- Definition

Tax effect on the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References+ Details