Nuclear Decommissioning Trust Fund Investments (Fair Values Of Investments In Debt And Equity Securities In Nuclear Decommissioning Trust Fund) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	$ 341	$ 316
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	226	237
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	11	4
Fair Value	556	549
Debt Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	191	175
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	2	7
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	4	0
Fair Value	189	182
Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	147	138
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	224	230
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	7	4
Fair Value	364	364
Cash
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	4	1
Fair Value	4	1
Other Debt And Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	(1)	2
Fair Value	$ (1)	$ 2

Nuclear Decommissioning Trust Fund Investments [Line Items]

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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-Topic 320
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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-Topic 320
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 320
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-Publisher FASB
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Decommission fund to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Decommission fund investment for the process whereby a power station, at the end of its economic life, is taken permanently out of service and its site made available for other purposes. In the case of a nuclear station this comprises three different states of clearance. Immediately after the final closure, radioactive material such as nuclear fuel and operational waste is removed and the buildings surrounding the reactor shield are dismantled and finally the reactor itself is dismantled.

+ 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 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 12
-Article 5

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