Balance Sheet Components Investments Held in Trust (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Marketable securities, at fair value:
Decommissioning Fund Investments, Fair Value	$ 41	$ 40
Non-qualified benefit plan trust	34	33
Nuclear Decommissioning [Member]
Cash equivalents	21	18
Marketable securities, at fair value:
Equity securities	0	0
Debt securities	20	22
Insurance contracts, at cash surrender value	0	0
Decommissioning Fund Investments, Fair Value	41	40
Non Qualified Benefit Plans [Member]
Cash equivalents	1	1
Marketable securities, at fair value:
Equity securities	6	5
Debt securities	1	1
Insurance contracts, at cash surrender value	26	26
Non-qualified benefit plan trust	$ 34	$ 33

The amount of cash, securities, or other assets held by a third-party trustee pursuant to the terms of an agreement which assets are available to be used by beneficiaries to that agreement only within the specific terms thereof and which agreement is expected to terminate more than one year from the balance sheet date (or operating cycle, if longer) at which time the assets held-in-trust will be released or forfeited.

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-Subparagraph (SX 210.4-08.(b))
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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-Name Accounting Standards Codification
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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Fair value portion of the amount that could be realized under a life insurance contract or contracts owned by the entity, commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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For an unclassified balance sheet, this item represents investments in common and preferred stocks and other forms of securities that provide ownership interests in a corporation.

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