Represents the net gain (loss) from the increase (decrease) in the fair value of derivative instrument not designated as hedging instrument, recognized on the balance sheet as regulatory (assets)/liabilities.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Net gain (loss) from the increase (decrease) in fair value of derivative instrument not designated as hedging instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph b(1)(b)

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- Definition

The estimated net amount of unrealized gains or losses on price risk cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph b(2)

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Risk Management and Derivative Financial Instruments (Details 2) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2010 Electric Commodity contracts Derivatives in Cash Flow Hedging Relationships	Sep. 30, 2010 Electric Commodity contracts Derivatives in Cash Flow Hedging Relationships	Dec. 31, 2011 Electric Commodity contracts Derivatives in Cash Flow Hedging Relationships	Dec. 31, 2010 Electric Commodity contracts Derivatives in Cash Flow Hedging Relationships	Sep. 30, 2011 Electric Commodity contracts Derivatives in Cash Flow Hedging Relationships	Sep. 30, 2010 Electric Derivatives in Cash Flow Hedging Relationships	Sep. 30, 2010 Electric Derivatives in Cash Flow Hedging Relationships	Dec. 31, 2011 Electric Derivatives in Cash Flow Hedging Relationships	Dec. 31, 2010 Electric Derivatives in Cash Flow Hedging Relationships	Sep. 30, 2011 Electric Commodity contracts	Sep. 30, 2010 Electric Commodity contracts	Sep. 30, 2011 Electric Commodity contracts	Sep. 30, 2010 Electric Commodity contracts	Sep. 30, 2011 Electric Commodity contracts	Sep. 30, 2010 Electric Commodity contracts	Sep. 30, 2011 Gas Commodity contracts	Sep. 30, 2010 Gas Commodity contracts	Sep. 30, 2011 Gas Commodity contracts	Sep. 30, 2010 Gas Commodity contracts	Sep. 30, 2011 Gas Commodity contracts	Sep. 30, 2010 Gas Commodity contracts	Sep. 30, 2011 Electric	Sep. 30, 2010 Electric	Sep. 30, 2011 Electric	Sep. 30, 2010 Electric	Sep. 30, 2011 Electric	Sep. 30, 2010 Electric	Sep. 30, 2011 Gas	Sep. 30, 2010 Gas	Sep. 30, 2011 Gas	Sep. 30, 2010 Gas	Sep. 30, 2011 Gas	Sep. 30, 2010 Gas
Gain / (Loss) on derivatives
Unrealized losses applicable to financial instruments which will settle in next twelve months					$ 2,900,000
Amount of Gain / (Loss) Reclassed from OCI into Income (Effective portion)	(4,864,000)	(5,814,000)		(6,703,000)		(4,864,000)	(5,814,000)		(6,703,000)
Amount of Gain / (Loss) Recognized in OCI on Derivative (Effective portion)	(1,934,000)	(7,258,000)	(896,000)	(9,278,000)		(1,934,000)	(7,258,000)	(896,000)	(9,278,000)
Amount of (Loss) on Derivative recognized as Regulatory (assets)/liabilities										(2,022,000)	(1,646,000)	(2,758,000)	(3,384,000)	(3,165,000)	(3,840,000)	(572,000)	(602,000)	(842,000)	(781,000)	(688,000)	(283,000)	(2,022,000)	(1,646,000)	(2,758,000)	(3,384,000)	(3,165,000)	(3,840,000)	(572,000)	(602,000)	(842,000)	(781,000)	(688,000)	(283,000)
Amount of (Loss) Recognized in Fuel and purchased power expense										$ (966,000)	$ (363,000)	$ (1,358,000)	$ (760,000)	$ (1,441,000)	$ (859,000)							$ (966,000)	$ (363,000)	$ (1,358,000)	$ (760,000)	$ (1,441,000)	$ (859,000)