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Derivative and Hedging Instruments (Details-1) (USD $) In Thousands, unless otherwise specified |  |  |  |  |  | 12 Months Ended |  |  |  |  |  |  |  |  | 12 Months Ended |  |  |  |  |  |  |  |  |  |
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Dec. 31, 2013 Other Current Assets [Member] | Dec. 31, 2012 Other Current Assets [Member] | Dec. 31, 2011 Other Current Assets [Member] | Dec. 31, 2013 Commodity Contracts and Financial Transimission Rights [Member] | Dec. 31, 2012 Commodity Contracts and Financial Transimission Rights [Member] | Dec. 31, 2013 Commodity Derivative Contracts [Member] MWh Dth | Dec. 31, 2012 Commodity Derivative Contracts [Member] MWh Dth | Dec. 31, 2013 Commodity Derivative Contracts [Member] Other Current Assets [Member] | Dec. 31, 2012 Commodity Derivative Contracts [Member] Other Current Assets [Member] | Dec. 31, 2013 Commodity Derivative Contracts [Member] Other Deferred Charges [Member] | Dec. 31, 2012 Commodity Derivative Contracts [Member] Other Deferred Charges [Member] | Dec. 31, 2013 Commodity Derivative Contracts [Member] Derivative Liability (Current) [Member] | Dec. 31, 2012 Commodity Derivative Contracts [Member] Derivative Liability (Current) [Member] | Dec. 31, 2013 Commodity Derivative Contracts [Member] Derivative Liability (Long-term) [Member] | Dec. 31, 2012 Commodity Derivative Contracts [Member] Derivative Liability (Long-term) [Member] | Dec. 31, 2013 Energy Related Commodity Contract [Member] Cash Flow Hedging [Member] | Dec. 31, 2013 Financial Transmission Rights [Member] MW | Dec. 31, 2012 Financial Transmission Rights [Member] MW | Dec. 31, 2013 Financial Transmission Rights [Member] Other Current Assets [Member] | Dec. 31, 2012 Financial Transmission Rights [Member] Other Current Assets [Member] | Dec. 31, 2013 Financial Transmission Rights [Member] Derivative Liability (Current) [Member] | Dec. 31, 2012 Financial Transmission Rights [Member] Derivative Liability (Current) [Member] | Dec. 31, 2013 Ten-year PPA [Member] | Dec. 31, 2012 Ten-year PPA [Member] | Dec. 31, 2013 Ten-year PPA [Member] Derivative Liability (Current) [Member] | Dec. 31, 2012 Ten-year PPA [Member] Derivative Liability (Current) [Member] | Dec. 31, 2013 Ten-year PPA [Member] Derivative Liability (Long-term) [Member] | Dec. 31, 2012 Ten-year PPA [Member] Derivative Liability (Long-term) [Member]
Derivatives Fair Value [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum term of derivative hedging contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |
Gross Notional Volume of Open Derivatives |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount, energy measure (in MWh) |  |  |  |  |  | 458,660 | 444,650 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount, decatherm measure (in Dth) |  |  |  |  |  | 3,750,000 | 1,980,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount, power measure (in MW) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,984 | 2,670 |  |  |  |  |  |  |  |  |  |
Derivative Fair Values [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative fair value, net | $ 411 | $ 574 | $ 1,604 | $ 1,800 | $ 300 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (65,700) | $ (72,600) |  |  |  |
Derivative fair value, gross asset |  |  |  |  |  | 1,523 | 460 | 1,356 | 365 | 167 | 95 |  |  |  |  |  | 363 | 206 | 363 | 206 |  |  |  |  |  |  |  |
Derivative fair value, gross liability |  |  |  |  |  | $ 99 | $ 405 |  |  |  |  | $ 51 | $ 394 | $ 48 | $ 11 |  |  |  |  |  | $ 0 | $ 0 | $ 65,680 | $ 72,590 | $ 7,750 | $ 9,270 | $ 57,930 | $ 63,320

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