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Commitments, Guarantees and Contingencies - Environmental Matters (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($) MW
Ozone NAAQS [Member]
Environmental Matters [Line Items]
Estimated Environmental Compliance Costs	$ 0.0
Minimum [Member] | Coal Combustion Residuals [Member]
Environmental Matters [Line Items]
Estimated Environmental Compliance Costs	65.0
Maximum [Member] | Clean Water Act - Aquatic Organisms [Member]
Environmental Matters [Line Items]
Estimated Environmental Compliance Costs	15.0
Maximum [Member] | Coal Combustion Residuals [Member]
Environmental Matters [Line Items]
Estimated Environmental Compliance Costs	$ 100.0
NOV Consent Decree [Member]
Environmental Matters [Line Items]
Additional Wind Generating Capacity (MW) | MW	200

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[Line Items] for Environmental Matters [Table]

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Capacity of a generating facility, unit, or project in megawatts.

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Amount of loss exposure accrued and the best estimate of reasonably possible loss exposure in excess of the accrual.

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Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (c),(d)(2)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

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