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The Effect of Derivative Instruments on the Consolidated Statement of Income (Details) (Price Swaps, Derivative in Cash Flow Hedging Relationship, Natural Gas, USD $)
In Thousands, unless otherwise specified |
3 Months Ended | 6 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2013
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Jun. 30, 2012
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Mar. 31, 2013
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Dec. 31, 2012
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Mar. 31, 2012
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Dec. 31, 2011
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| Derivative Instruments, Gain (Loss) [Line Items] | ||||||||
| Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax | $ 71,674 | $ 132,731 | $ 71,674 | $ 132,731 | $ 76,761 | $ 35,453 | $ 151,780 | $ 179,915 |
| Amount of Gain (Loss) Recognized in OCI on Derivative | 45,749 | 10,663 | 27,154 | 86,739 | ||||
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Outside Sales
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| Derivative Instruments, Gain (Loss) [Line Items] | ||||||||
| Amount of Gain (Loss) Reclassified from Accumulated OCI into Income | 9,528 | 57,847 | 32,241 | 105,788 | ||||
| Derivative Instruments, Gain (Loss) Recognized in Income, Net | $ (3,753) | $ 882 | $ (2,712) | $ 47 | ||||