v2.4.1.9

Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Cash and Cash Equivalents Items [Line Items]
Current	$ 195us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue	$ 203us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue
Non-current	49us-gaap_RestrictedCashAndCashEquivalentsNoncurrent	69us-gaap_RestrictedCashAndCashEquivalentsNoncurrent
Total	244us-gaap_RestrictedCashAndCashEquivalents	272us-gaap_RestrictedCashAndCashEquivalents
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Cash and cash equivalents subject to project finance facilities and lease agreements	257cpn_CashAndCashEquivalentsSubjectToProjectFinanceFacilitiesAndLeaseAgreements	292cpn_CashAndCashEquivalentsSubjectToProjectFinanceFacilitiesAndLeaseAgreements
Property, plant and equipment, salvage value (as a percent)	10.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
Property, plant and equipment, salvage value of rotables (as a percent)	0.15%cpn_PropertyPlantAndEquipmentSalvageValuePercentageRotables
Osprey Energy Center Agreement Term	0 years 27 months
Impairment losses	123us-gaap_AssetImpairmentCharges	16us-gaap_AssetImpairmentCharges	0us-gaap_AssetImpairmentCharges
Asset retirement obligations	47us-gaap_AssetRetirementObligation	44us-gaap_AssetRetirementObligation
Freestone Energy Center [Member]
Jointly Owned Plants [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share	75.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_FreestoneEnergyCenterMember
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	389us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_FreestoneEnergyCenterMember
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(140)us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_FreestoneEnergyCenterMember
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_FreestoneEnergyCenterMember
Hidalgo Energy Center [Member]
Jointly Owned Plants [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share	78.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_HidalgoEnergyCenterMember
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	257us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_HidalgoEnergyCenterMember
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(104)us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_HidalgoEnergyCenterMember
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress / us-gaap_JointlyOwnedUtilityPlantAxis = cpn_HidalgoEnergyCenterMember
Debt Service
Restricted Cash and Cash Equivalents Items [Line Items]
Current	10us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember	11us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember
Non-current	25us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember	41us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember
Total	35us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember	52us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_DebtServiceMember
Rent Reserve [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Current	4us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember	3us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember
Non-current	0us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember	0us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember
Total	4us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember	3us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_RentReserveMember
Construction Major Maintenance
Restricted Cash and Cash Equivalents Items [Line Items]
Current	54us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember	35us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember
Non-current	17us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember	20us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember
Total	71us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember	55us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_ConstructionMajorMaintenanceMember
Security Project Insurance
Restricted Cash and Cash Equivalents Items [Line Items]
Current	127us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember	151us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember
Non-current	5us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember	6us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember
Total	132us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember	157us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_SecurityProjectInsuranceMember
Other
Restricted Cash and Cash Equivalents Items [Line Items]
Current	0us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember	3us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember
Non-current	2us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember	2us-gaap_RestrictedCashAndCashEquivalentsNoncurrent / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember
Total	$ 2us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember	$ 5us-gaap_RestrictedCashAndCashEquivalents / us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsAxis = cpn_OtherRestrictedCashMember
Greenfield [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Ownership percentage in equity method investment	50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_GreenfieldMember
Whitby [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Ownership percentage in equity method investment	50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_WhitbyMember

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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