v2.4.1.9

SONGS NDT 1 (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | $ 685 us-gaap_AvailableForSaleSecuritiesAmortizedCost |  |  |  | $ 675 us-gaap_AvailableForSaleSecuritiesAmortizedCost
Gross Unrealized Gains | 477 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains |  |  |  | 466 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains
Gross Unrealized Loss | (12)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss |  |  |  | (10)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss
Estimated fair value | 1,150 us-gaap_AvailableForSaleSecurities |  |  |  | 1,131 us-gaap_AvailableForSaleSecurities
Proceeds from sales | 94 us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds | [1] | 195 us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds | [1] |
Gross realized gains | 2 us-gaap_AvailableForSaleSecuritiesGrossRealizedGains |  | 4 us-gaap_AvailableForSaleSecuritiesGrossRealizedGains |  |
Gross realized losses | (4)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses |  | (4)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses |  |
Total Debt Securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 448 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |  |  |  | 430 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember
Gross Unrealized Gains | 25 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |  |  |  | 21 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember
Gross Unrealized Loss | (8)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |  |  |  | (6)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember
Estimated fair value | 465 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember |  |  |  | 445 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_DebtSecuritiesMember
Debt Securities Issued By The U.S. Treasury And Other U.S. Government Corporations And Agencies |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 103 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | [2] |  |  | 103 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Gross Unrealized Gains | 8 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | [2] |  |  | 6 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Gross Unrealized Loss | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | [2] |  |  | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Estimated fair value | 111 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember | [2] |  |  | 109 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USTreasuryAndGovernmentMember
Municipal Bonds |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 134 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | [3] |  |  | 121 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Gross Unrealized Gains | 8 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | [3] |  |  | 8 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Gross Unrealized Loss | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | [3] |  |  | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Estimated fair value | 142 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember | [3] |  |  | 129 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_USStatesAndPoliticalSubdivisionsMember
Other Debt Securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 211 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember | [4] |  |  | 206 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember
Gross Unrealized Gains | 9 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember | [4] |  |  | 7 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember
Gross Unrealized Loss | (8)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember | [4] |  |  | (6)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember
Estimated fair value | 212 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember | [4] |  |  | 207 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_OtherDebtSecuritiesMember
Equity Securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 218 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |  |  |  | 215 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Gross Unrealized Gains | 452 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |  |  |  | 444 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Gross Unrealized Loss | (4)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |  |  |  | (4)us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Estimated fair value | 666 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember |  |  |  | 655 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_EquitySecuritiesMember
Cash And Cash Equivalents |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Cost | 19 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember |  |  |  | 30 us-gaap_AvailableForSaleSecuritiesAmortizedCost / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember
Gross Unrealized Gains | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember |  |  |  | 1 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember
Gross Unrealized Loss | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember |  |  |  | 0 us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember
Estimated fair value | $ 19 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember |  |  |  | $ 31 us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashAndCashEquivalentsMember
[1] | Excludes securities that are held to maturity.
[2] | Maturity dates are 2015-2060.
[3] | Maturity dates are 2015-2114.
[4] | Maturity dates are 2015-2111.

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