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Balance Sheet Components (Tables) | 12 Months Ended
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Dec. 31, 2016
Balance Sheet Components [Abstract] |
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] | The following is the activity in the allowance for uncollectible accounts (in millions):
| Years Ended December 31,
| 2016 |  | 2015 |  | 2014
Balance as of beginning of year | $ | 6 |  |  | $ | 6 |  |  | $ | 6 |
Increase in provision | 5 |  |  | 6 |  |  | 6 |
Amounts written off, less recoveries | (5 | ) |  | (6 | ) |  | (6 | )
Balance as of end of year | $ | 6 |  |  | $ | 6 |  |  | $ | 6 |
Investments held in trust [Table Text Block] | The trusts are comprised of the following investments as of December 31 (in millions):
| Nuclear Decommissioning Trust |  | Non-Qualified Benefit Plan Trust
| 2016 |  | 2015 |  | 2016 |  | 2015
Cash equivalents | $ | 21 |  |  | $ | 18 |  |  | $ | 1 |  |  | $ | 1 |
Marketable securities, at fair value: |  |  |  |  |  |  |
Equity securities | — |  |  | — |  |  | 6 |  |  | 5 |
Debt securities | 20 |  |  | 22 |  |  | 1 |  |  | 1 |
Insurance contracts, at cash surrender value | — |  |  | — |  |  | 26 |  |  | 26 |
| $ | 41 |  |  | $ | 40 |  |  | $ | 34 |  |  | $ | 33 |
Schedule of Other Assets and Other Liabilities [Table Text Block] | Other current assets and Accrued expenses and other current liabilities consist of the following (in millions):
| As of December 31,
| 2016 |  | 2015
Other current assets: |  |  |
Prepaid expenses | $ | 48 |  |  | $ | 43 |
Margin deposits | 8 |  |  | 33 |
Assets from price risk management activities | 18 |  |  | 10 |
Other | 3 |  |  | 2 |
| $ | 77 |  |  | $ | 88 |
Accrued expenses and other current liabilities: |  |  |
Regulatory liabilities—current | $ | 51 |  |  | $ | 55 |
Accrued employee compensation and benefits | 52 |  |  | 51 |
Accrued interest payable | 25 |  |  | 25 |
Accrued dividends payable | 30 |  |  | 28 |
Accrued taxes payable | 25 |  |  | 25 |
Other | 71 |  |  | 75 |
| $ | 254 |  |  | $ | 259 |

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- Definition Balance Sheet Components [Abstract] + References No definition available. + Details
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- Definition investments held in trust [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of assets and liabilities, classified as other. + References No definition available. + Details
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- Definition The entire disclosure for any allowance and reserve accounts (their beginning and ending balances, as well as a reconciliation by type of activity during the period). Alternatively, disclosure of the required information may be within the footnotes to the financial statements or a supplemental schedule to the financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690 + Details
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