Organization and Basis of Presentation (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Regulatory assets on the Balance Sheets
Regulatory Assets	$ 40	$ 1,014
Regulatory Liability	(2,720)	(157)
Net Regulatory Assets (Liabilities) included on the Consolidated Balance Sheets	(2,680)	857
Increase (Decrease)	(3,537)
Regulatory transition costs
Regulatory assets on the Balance Sheets
Regulatory Assets	46	90
Increase (Decrease)	(44)
Customer receivables (payables) for future income taxes
Regulatory assets on the Balance Sheets
Regulatory Assets	(2,765)	468
Increase (Decrease)	(3,233)
Nuclear decommissioning and spent fuel disposal costs
Regulatory assets on the Balance Sheets
Regulatory Liability	(323)	(304)
Increase (Decrease)	(19)
Asset removal costs
Regulatory assets on the Balance Sheets
Regulatory Liability	(774)	(770)
Increase (Decrease)	(4)
Deferred transmission costs
Regulatory assets on the Balance Sheets
Regulatory Assets	187	122
Increase (Decrease)	65
Deferred generation costs
Regulatory assets on the Balance Sheets
Regulatory Assets	198	331
Increase (Decrease)	(133)
Deferred distribution costs
Regulatory assets on the Balance Sheets
Regulatory Assets	258	296
Increase (Decrease)	(38)
Contract valuations
Regulatory assets on the Balance Sheets
Regulatory Assets	118	153
Increase (Decrease)	(35)
Storm-related costs
Regulatory assets on the Balance Sheets
Regulatory Assets	329	397
Increase (Decrease)	(68)
Other
Regulatory assets on the Balance Sheets
Regulatory Assets	46	$ 74
Increase (Decrease)	$ (28)

The increase (decrease) during the reporting period in the value of assets that are created when regulatory agencies permits public utilities to defer costs (revenues) to the balance sheet. This element is a the increase (decrease) of regulatory assets and liabilities combined.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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The net amount of all regulatory assets less all regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

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The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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