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Other Investments | 6 Months Ended
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Jun. 30, 2013
Regulated Entity, Other Assets, Noncurrent [Abstract] |
Other Investments | Other Investments Nuclear Decommissioning Trusts Future decommissioning costs of removal of SCE's nuclear assets are expected to be funded from independent decommissioning trusts, which currently receive contributions of approximately $23 million per year through SCE customer rates. The following table sets forth amortized cost and fair value of the trust investments:
| Longest Maturity Dates |  | Amortized Cost |  | Fair Value
(in millions) |  | June 30, 2013 |  | December 31, 2012 |  | June 30, 2013 |  | December 31, 2012
Stocks | — |  | $ | 728 |  |  | $ | 978 |  |  | $ | 2,085 |  |  | $ | 2,271 |
Municipal bonds | 2051 |  | 504 |  |  | 518 |  |  | 592 |  |  | 644 |
U.S. government and agency securities | 2043 |  | 975 |  |  | 547 |  |  | 1,025 |  |  | 603 |
Corporate bonds | 2054 |  | 293 |  |  | 324 |  |  | 347 |  |  | 410 |
Short-term investments, primarily cash equivalents | One-year |  | 274 |  |  | 117 |  |  | 280 |  |  | 121 |
Total investments |  |  | 2,774 |  |  | 2,484 |  |  | 4,329 |  |  | 4,049 |
Net payables |  |  | (148 | ) |  | (1 | ) |  | (148 | ) |  | (1 | )
Total nuclear decommissioning trusts |  |  | $ | 2,626 |  |  | $ | 2,483 |  |  | $ | 4,181 |  |  | $ | 4,048 |
Trust fund earnings (based on specific identification) increase the trust fund balance and the ARO regulatory liability. Proceeds from sales of securities (which are reinvested) were $1.5 billion and $496 million for the three months ended June 30, 2013 and 2012, respectively and $2.0 billion and $1.1 billion for the six months ended June 30, 2013 and 2012, respectively. Unrealized holding gains, net of losses, were $1.3 billion and $1.6 billion at June 30, 2013 and December 31, 2012, respectively. The following table sets forth a summary of changes in the fair value of the trust:
| Three months ended June 30, |  | Six months ended June 30,
(in millions) | 2013 |  | 2012 |  | 2013 |  | 2012
Balance at beginning of period | $ | 4,246 |  |  | $ | 3,853 |  |  | $ | 4,048 |  |  | $ | 3,592 |
Gross realized gains | 137 |  |  | 15 |  |  | 142 |  |  | 40 |
Gross realized losses | (1 | ) |  | (1 | ) |  | (2 | ) |  | (5 | )
Unrealized gains (losses), net | (185 | ) |  | (67 | ) |  | (9 | ) |  | 116 |
Other-than-temporary impairments | (21 | ) |  | (19 | ) |  | (29 | ) |  | (23 | )
Interest, dividends, contributions and other | 5 |  |  | 29 |  |  | 31 |  |  | 90 |
Balance at end of period | $ | 4,181 |  |  | $ | 3,810 |  |  | $ | 4,181 |  |  | $ | 3,810 |
Due to regulatory mechanisms, earnings and realized gains and losses (including other-than-temporary impairments) have no impact on operating revenue or earnings.

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