v3.6.0.2

SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | $ 658 | $ 660 |
Gross unrealized gains | 372 | 423 |
Gross unrealized losses | (4) | (20) |
Estimated fair value | 1,026 | 1,063 |
Proceeds from sales | 1,134 | 577 | $ 601
Gross realized gains | 111 | 29 | 11
Gross realized losses | (29) | (15) | $ (11)
Debt Securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 396 | 431 |
Gross unrealized gains | 6 | 11 |
Gross unrealized losses | (3) | (13) |
Estimated fair value | 399 | 429 |
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 52 | 89 |
Gross unrealized gains | 0 | 2 |
Gross unrealized losses | 0 | 0 |
Estimated fair value | 52 | 91 |
Municipal bonds [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 203 | 148 |
Gross unrealized gains | 4 | 8 |
Gross unrealized losses | (1) | 0 |
Estimated fair value | 206 | 156 |
Other securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 141 | 194 |
Gross unrealized gains | 2 | 1 |
Gross unrealized losses | (2) | (13) |
Estimated fair value | 141 | 182 |
Equity securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 143 | 214 |
Gross unrealized gains | 366 | 412 |
Gross unrealized losses | (1) | (7) |
Estimated fair value | 508 | 619 |
Cash and cash equivalents [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Cost | 119 | 15 |
Gross unrealized gains | 0 | 0 |
Gross unrealized losses | 0 | 0 |
Estimated fair value | $ 119 | $ 15 |

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