CONTINGENCIES - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011 LegalMatter
Securities Class Actions
Loss Contingencies [Line Items]
Number of lawsuits filed	3
Securities Class Actions First Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	March 9, 2010
Securities Class Actions Second Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	March 18, 2010
Securities Class Actions Third Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	April 7, 2010
Stockholder Derivative Cases
Loss Contingencies [Line Items]
Number of lawsuits filed	4
Stockholder Derivative Cases For County Of Washoe
Loss Contingencies [Line Items]
Number of lawsuits filed	2
Descriptions of derivative cases filed	The two stockholder derivative cases filed in the Second Judicial District Court of the State of Nevada were consolidated by the Court in an order dated May 27, 2010
Descriptions of derivative cases filed by plaintiff	Filed a consolidated derivative complaint on September 7, 2010
Descriptions of derivative cases filed by defendant	In accordance with a stipulation between the parties, filed a motion to dismiss on November 16, 2010.
Stockholder Derivative Cases For District Of Nevada
Loss Contingencies [Line Items]
Number of lawsuits filed	2
Descriptions of derivative cases filed	The two stockholder derivative cases filed in the United States District Court for the District of Nevada were consolidated by the Court in an order dated August 31, 2010
Descriptions of derivative cases filed by plaintiff	Filed a consolidated derivative complaint on October 28, 2010.
Descriptions of derivative cases filed by defendant	The Company filed a motion to dismiss on December 13, 2010.
Stockholder Derivative Cases For County Of Washoe First Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	March 16, 2010
Stockholder Derivative Cases For County Of Washoe Second Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	April 21, 2010
Stockholder Derivative Cases For District Of Nevada First Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	March 29, 2010
Stockholder Derivative Cases For District Of Nevada Second Lawsuit
Loss Contingencies [Line Items]
Lawsuit filing date	June 7, 2010
Pending or Threatened Litigation
Loss Contingencies [Line Items]
Refund to customers equaling the time value of the revenues collected during the periods of non-compliance with FERC's requirements for QF status	1.6

This element represents the gross amount awarded, to be received by, or to be remitted to the entity in settlement of litigation occurring during the period.

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- Definition

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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Describes important rulings or decisions made by the judge, arbitrator or mediator in the legal matter that could impact the outcome of the case.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (a)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 450

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Describe actions taken by the defendant in the legal matter.

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Describes actions taken or threatened by the plaintiff in the legal matter.

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States the date the complaint was formally filed in a court of law, in arbitration or mediation.

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The total number of new claims filed pertaining to a loss contingency during the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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