v3.8.0.1

SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2018 | Mar. 31, 2018 | Mar. 31, 2017 | Jan. 31, 2018 | Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Anticipated term of dismantlement work |  | 10 years |  |  |
Cost | $ 697 | $ 697 |  |  | $ 701
Gross unrealized gains | 327 | 327 |  |  | 336
Gross unrealized losses | (7) | (7) |  |  | (4)
Estimated fair value | 1,017 | 1,017 |  |  | 1,033
Proceeds from sales |  | 210 | $ 357 |  |
Gross realized gains |  | 4 | 45 |  |
Gross realized losses |  | (3) | $ (5) |  |
Total debt securities [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 506 | 506 |  |  | 514
Gross unrealized gains | 6 | 6 |  |  | 10
Gross unrealized losses | (5) | (5) |  |  | (3)
Estimated fair value | 507 | 507 |  |  | 521
U.S. government corporations and agencies [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 44 | 44 |  |  | 54
Gross unrealized gains | 0 | 0 |  |  | 0
Gross unrealized losses | 0 | 0 |  |  | 0
Estimated fair value | 44 | 44 |  |  | 54
Municipal bonds [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 245 | 245 |  |  | 245
Gross unrealized gains | 4 | 4 |  |  | 7
Gross unrealized losses | (2) | (2) |  |  | (2)
Estimated fair value | 247 | 247 |  |  | 250
Other securities [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 217 | 217 |  |  | 215
Gross unrealized gains | 2 | 2 |  |  | 3
Gross unrealized losses | (3) | (3) |  |  | (1)
Estimated fair value | 216 | 216 |  |  | 217
Equity securities [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 172 | 172 |  |  | 171
Gross unrealized gains | 321 | 321 |  |  | 326
Gross unrealized losses | (2) | (2) |  |  | (1)
Estimated fair value | 491 | 491 |  |  | 496
Cash and cash equivalents [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 19 | 19 |  |  | 16
Gross unrealized gains | 0 | 0 |  |  | 0
Gross unrealized losses | 0 | 0 |  |  | 0
Estimated fair value | $ 19 | $ 19 |  |  | $ 16
San Diego Gas and Electric Company [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Percent of dismantlement work expense | 20.00% | 20.00% |  |  |
Authorized recovery amount, nuclear decommissioning trust funding | $ 362 | $ 362 |  | $ 60 |
SONGS 1 Decommissioning [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Environmental exit costs, anticipated cost | 207 |  |  |  |
SONGS 1 Decommissioning [Member] | San Diego Gas and Electric Company [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Environmental exit costs, anticipated cost | 41 |  |  |  |
Environmental Exit Costs, Anticipated Internal Costs | 3 |  |  |  |
SONGS 2 and 3 Decommissioning [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Environmental exit costs, anticipated cost | 3,200 |  |  |  |
SONGS 2 and 3 Decommissioning [Member] | San Diego Gas and Electric Company [Member] |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Environmental exit costs, anticipated cost | 638 |  |  |  |
Environmental Exit Costs, Anticipated Internal Costs | $ 43 |  |  |  |

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