v2.4.1.9
Derivative Instruments (Detail 5) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Derivative Instruments Subject to Master Netting Arrangement [Line Items]    
Derivative Asset, Fair Value, Gross Asset $ 2,569us-gaap_DerivativeFairValueOfDerivativeAsset $ 2,497us-gaap_DerivativeFairValueOfDerivativeAsset
Derivative Asset, Fair Value, Amount Not Offset Against Collateral (2,073)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction (2,087)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
Derivative, Collateral, Obligation to Return Cash (228)us-gaap_DerivativeCollateralObligationToReturnCash [1] (269)us-gaap_DerivativeCollateralObligationToReturnCash [1]
Derivative Liability, Fair Value, Gross Liability (2,215)us-gaap_DerivativeFairValueOfDerivativeLiability (2,226)us-gaap_DerivativeFairValueOfDerivativeLiability
Derivative Liability, Fair Value, Amount Not Offset Against Collateral 2,073us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction 2,087us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
Derivative, Collateral, Right to Reclaim Cash 14us-gaap_DerivativeCollateralRightToReclaimCash [1] 15us-gaap_DerivativeCollateralRightToReclaimCash [1]
Derivative, Fair Value, Net 354us-gaap_DerivativeFairValueOfDerivativeNet 271us-gaap_DerivativeFairValueOfDerivativeNet
Derivative Fair Value, Amount Not Offset Against Collateral, Net 0cpn_DerivativeFairValueAmountNotOffsetAgainstCollateralNet 0cpn_DerivativeFairValueAmountNotOffsetAgainstCollateralNet
Margin/Cash (Received) Posted Subject to Master Netting Arrangement (214)cpn_DerivativeCollateralRightToReclaimCashNet [1] (254)cpn_DerivativeCollateralRightToReclaimCashNet [1]
Derivative Asset, Fair Value, Amount Offset Against Collateral 268us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral 141us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
Derivative Liability, Fair Value, Amount Offset Against Collateral (128)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral (124)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
Derivative, Fair Value, Amount Offset Against Collateral, Net 140cpn_DerivativeAssetFairValueAmountOffsetAgainstCollateralNetOfDerivativeLiabilityFairValueAmountOffsetAgainstCollateral 17cpn_DerivativeAssetFairValueAmountOffsetAgainstCollateralNetOfDerivativeLiabilityFairValueAmountOffsetAgainstCollateral
Commodity Exchange Traded Futures and Swaps Contracts [Member]    
Derivative Instruments Subject to Master Netting Arrangement [Line Items]    
Derivative Asset, Fair Value, Gross Asset 2,037us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 2,134us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Derivative Asset, Fair Value, Amount Not Offset Against Collateral (1,810)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 (1,865)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Derivative, Collateral, Obligation to Return Cash (227)us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 [1] (269)us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 [1]
Derivative Liability, Fair Value, Gross Liability (1,814)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 (1,870)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Derivative Liability, Fair Value, Amount Not Offset Against Collateral 1,810us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 1,865us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Derivative, Collateral, Right to Reclaim Cash 4us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 [1] 5us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 [1]
Derivative Asset, Fair Value, Amount Offset Against Collateral 0us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 0us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Derivative Liability, Fair Value, Amount Offset Against Collateral 0us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember		 0us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityExchangeTradedFuturesAndSwapsContractsMember
Commodity Forward Contract [Member]    
Derivative Instruments Subject to Master Netting Arrangement [Line Items]    
Derivative Asset, Fair Value, Gross Asset 528us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 359us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Derivative Asset, Fair Value, Amount Not Offset Against Collateral (263)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 (222)us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Derivative, Collateral, Obligation to Return Cash (1)us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 [1] 0us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 [1]
Derivative Liability, Fair Value, Gross Liability (283)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 (242)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Derivative Liability, Fair Value, Amount Not Offset Against Collateral 263us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 222us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Derivative, Collateral, Right to Reclaim Cash 10us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 [1] 10us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 [1]
Derivative Asset, Fair Value, Amount Offset Against Collateral 264us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 137us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Derivative Liability, Fair Value, Amount Offset Against Collateral (10)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember		 (10)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_CommodityForwardContractMember
Interest Rate Swap [Member]    
Derivative Instruments Subject to Master Netting Arrangement [Line Items]    
Derivative Asset, Fair Value, Gross Asset 4us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 4us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative Asset, Fair Value, Amount Not Offset Against Collateral 0us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 0us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative, Collateral, Obligation to Return Cash 0us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1] 0us-gaap_DerivativeCollateralObligationToReturnCash
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1]
Derivative Liability, Fair Value, Gross Liability (118)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 (114)us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative Liability, Fair Value, Amount Not Offset Against Collateral 0us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 0us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative, Collateral, Right to Reclaim Cash 0us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1] 0us-gaap_DerivativeCollateralRightToReclaimCash
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 [1]
Derivative, Fair Value, Net (114)us-gaap_DerivativeFairValueOfDerivativeNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 (110)us-gaap_DerivativeFairValueOfDerivativeNet
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative Asset, Fair Value, Amount Offset Against Collateral 4us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 4us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Derivative Liability, Fair Value, Amount Offset Against Collateral $ (118)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 $ (114)us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
[1] Negative balances represent margin deposits posted with us by our counterparties related to our derivative activities that are subject to a master netting arrangement. Positive balances reflect margin deposits and natural gas and power prepayments posted by us with our counterparties related to our derivative activities that are subject to a master netting arrangement. See Note 6 for a further discussion of our collateral.