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Fair Value of Financial Instruments Fair Value Options Quantitative Disclosure (Details) - USD ($) | Sep. 30, 2016 | Dec. 31, 2015
--- | --- | ---
Low [Member] |  |
Commodity Contracts |  |
Electricity physical forward | $ 15.58 | $ 8.50
Natural gas financial swaps | 1.84 | 2.06
Fnancial swaps - electricity | 19.29 | 9.98
High [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 41.79 | 84.47
Natural gas financial swaps | 3.23 | 3.70
Fnancial swaps - electricity | 33.75 | 27.36
Weighted Average [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 29.50 | 30.69
Natural gas financial swaps | 2.26 | 2.54
Fnancial swaps - electricity | 26.78 | 19.26
Assets [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 0 | 0
Natural gas financial swaps | 0 | 0
Fnancial swaps - electricity | 0 | 0
Total commodity contracts | 0 | 0
Liabilities [Member] |  |
Commodity Contracts |  |
Electricity physical forward | 139,000,000 | 105,000,000
Natural gas financial swaps | 21,000,000 | 14,000,000
Fnancial swaps - electricity | 0 | 0
Total commodity contracts | $ 160,000,000 | $ 119,000,000

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