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Nuclear Decommissioning Trust Fund (Tables) | 9 Months Ended
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Sep. 30, 2023
Regulated Operations [Abstract] |
Summary of aggregate fair values and unrealized gains and losses for the securities held in the trust fund | The following table summarizes the aggregate fair values and unrealized gains and losses for the securities held in the trust funds, as well as information about the contractual maturities of those securities. As of September 30, 2023, the trust funds are classified within non-current assets - held-for-sale on the Company's condensed consolidated balance sheet.
| As of September 30, 2023 |  | As of December 31, 2022
(In millions, except maturities) | Fair Value |  | Unrealized Gains |  | Unrealized Losses |  | Weighted-average Maturities (In years) |  | Fair Value |  | Unrealized Gains |  | Unrealized Losses |  | Weighted-average Maturities (In years)
Cash and cash equivalents | $ | 25 |  |  | $ | — |  |  | $ | — |  |  | — |  |  | $ | 15 |  |  | $ | — |  |  | $ | — |  |  | — |
U.S. government and federal agency obligations | 76 |  |  | — |  |  | 9 |  |  | 12 |  | 86 |  |  | — |  |  | 5 |  |  | 11
Federal agency mortgage-backed securities | 110 |  |  | — |  |  | 13 |  |  | 24 |  | 101 |  |  | — |  |  | 11 |  |  | 26
Commercial mortgage-backed securities | 31 |  |  | — |  |  | 4 |  |  | 29 |  | 35 |  |  | — |  |  | 4 |  |  | 30
Corporate debt securities | 111 |  |  | — |  |  | 11 |  |  | 12 |  | 114 |  |  | — |  |  | 13 |  |  | 12
Equity securities | 539 |  |  | 390 |  |  | — |  |  | — |  |  | 486 |  |  | 346 |  |  | 3 |  |  | — |
Foreign government fixed income securities | 1 |  |  | — |  |  | — |  |  | 14 |  | 1 |  |  | — |  |  | — |  |  | 17
Total | $ | 893 |  |  | $ | 390 |  |  | $ | 37 |  |  |  |  | $ | 838 |  |  | $ | 346 |  |  | $ | 36 |  |  |
Summary of proceeds from sales of available-for-sale securities and the related realized gains and losses | The following table summarizes proceeds from sales of available-for-sale securities held in the trust funds and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method.
| Nine months ended September 30,
(In millions) | 2023 |  | 2022
Realized gains | $ | 7 |  |  | $ | 12 |
Realized losses | (15) |  |  | (19) |
Proceeds from sale of securities | 280 |  |  | 363 |

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- Definition Tabular disclosure of the proceeds from sales of available-for-sale securities and the gross realized gains and gross realized losses that have been included in earnings as a result of those sales. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-9 + Details
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