v2.4.0.6

Related party transactions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Idaho Wind	Dec. 31, 2010 Idaho Wind	Dec. 31, 2011 ArcLight	Dec. 31, 2010 ArcLight	Dec. 31, 2009 ArcLight item
Related party transactions
Number of private equity funds					2
Aggregate amount payable on termination of contract					$ 15.0
Payment due on termination date for termination of agreement					6.0
Additional payment due on first anniversary of termination date				5.0
Additional payment due on second anniversary of termination date			3.0
Additional payment due on third anniversary of termination date			1.0
Estimated fair value of termination fee due			0.9
Loan to Idaho Wind		22.8
Interest income from loan given to Idaho Wind	$ 1.6

X

- Definition

Represents the number of private equity funds which are related parties.

+ References

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- Definition

Represents the estimated fair value of remaining liability associated with the termination fees.

+ References

No definition available.

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- Definition

Represents the additional payment due on first anniversary of the termination date.

+ References

No definition available.

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- Definition

Represents the additional payment due on second anniversary of the termination date.

+ References

No definition available.

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- Definition

Represents the amount due on the termination date of agreement.

+ References

No definition available.

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- Definition

Represents the additional payment due on third anniversary of the termination date.

+ References

No definition available.

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- Definition

The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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- Definition

Carrying amount as of the balance sheet date of obligations due all related parties.

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- Definition

The cash inflow from the collection of money previously advanced to an entity that is related to it but not strictly controlled.

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-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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