Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
Aug. 31, 2011	Dec. 31, 2011
Variable Interest Entities [Abstract]
Solar energy cost		$ 90
Operation commenced date	August 2011
Assets related to Pilesgrove		43
Additional financing obligation		$ 29

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Cost incurred in providing energy services during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(d))

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

+ Details

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Period Type:	duration

- Definition

The date the operations of the entity commenced.

+ References

No definition available.

+ Details

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- Definition

The carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5728-111685

+ Details

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Balance Type:	debit
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- Definition

The carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE).

+ References

+ Details

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