Asset retirement and environmental obligations.

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- Definition

Asset retirement obligations, cash flow estimates useful life extension.

+ References

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- Definition

Asset retirement obligations number of new obligations established.

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No definition available.

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- Definition

Decommission study period.

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No definition available.

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- Definition

Amount of asset retirement obligations incurred during the period.

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- Definition

Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

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- Definition

Amount of a decommissioning liability associated with a legal obligation that a firm incurs when it constructs or operates an asset that must eventually be withdrawn from active service. This may include operating assets such as nuclear power plants or shipping vessels.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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Accounting For Asset Retirement And Environmental Obligations - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($) obligation	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Asset Retirement And Environmental Obligations [Line Items]
Increase (decrease) in asset retirement obligations		$ (2,869)		$ 18,000
Asset Retirement Obligations, Number of New Obligations Established \| obligation	2
Increase to asset retirement cost	$ 8,569		$ 8,569
North Anna [Member]
Asset Retirement And Environmental Obligations [Line Items]
North Anna's nuclear decommissioning asset retirement obligation		$ 101,600	$ 97,600
Decommission study period		4 years
Asset retirement obligations cash flow estimates useful life		20 years