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Fair Value of Financial Instruments Fair Value Options Quantitative Disclosure (Details) - USD ($) | Mar. 31, 2016 | Dec. 31, 2015
--- | --- | ---
Low [Member] |  |
Commodity Contracts |  |
Electricity physical forward | $ 4.25 | $ 8.50
Natural gas financial swaps | 0.90 | 2.06
High [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 73.32 | 84.47
Natural gas financial swaps | 3.61 | 3.70
Weighted Average [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 29.16 | 30.69
Natural gas financial swaps | 2.46 | 2.54
Assets [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 0 | 0
Natural gas financial swaps | 0 | 0
Total commodity contracts | 0 | 0
Liabilities [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 117,000,000 | 105,000,000
Natural gas financial swaps | 14,000,000 | 14,000,000
Total commodity contracts | $ 131,000,000 | $ 119,000,000

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- Definition Electricity physical forward purchase + References No definition available. + Details
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