v2.4.1.9

Acquisitions, Divestitures and Discontinued Operations (Textuals) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 MW	Dec. 31, 2013 MW	Dec. 31, 2012	Dec. 27, 2012	Jul. 03, 2014	Sep. 30, 2014 MW
Business Acquisition [Line Items]
Power generation capacity	10,365cpn_PowerGenerationCapacity	9,427cpn_PowerGenerationCapacity
(Gain) on sale of power plants, net	$ 753us-gaap_GainLossOnDispositionOfAssets1	$ 0us-gaap_GainLossOnDispositionOfAssets1	$ 222us-gaap_GainLossOnDispositionOfAssets1
Fore River Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	809cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_ForeRiverEnergyCenterMember
Business Acquisition, Purchase Price Allocation, Assets Acquired	530us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = cpn_ForeRiverEnergyCenterMember
Guadalupe Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	1,050cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_GuadalupeEnergyCenterMember
Business Acquisition, Purchase Price Allocation, Assets Acquired	625us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = cpn_GuadalupeEnergyCenterMember
Guadalupe Expansion Capacity [Member]
Business Acquisition [Line Items]
Power generation capacity	400cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_GuadalupeExpansionCapacityMember
Business Acquisition, Purchase Price Allocation, Assets Acquired	15us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = cpn_GuadalupeExpansionCapacityMember
Bosque Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity		800cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_BosqueEnergyCenterMember
Business Acquisition, Purchase Price Allocation, Assets Acquired		432us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet / us-gaap_BusinessAcquisitionAxis = cpn_BosqueEnergyCenterMember
Block one power generation capacity		250cpn_BlockOnePowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_BosqueEnergyCenterMember
Block two power generation capacity		550cpn_BlockTwoPowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_BosqueEnergyCenterMember
Riverside Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity		603cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_RiversideEnergyCenterMember
Proceeds from Sale of Productive Assets		402us-gaap_ProceedsFromSaleOfProductiveAssets / us-gaap_BusinessAcquisitionAxis = cpn_RiversideEnergyCenterMember
Gain (Loss) on Disposition of Assets		7us-gaap_GainLossOnDispositionOfAssets / us-gaap_BusinessAcquisitionAxis = cpn_RiversideEnergyCenterMember
Broad River Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity		847cpn_PowerGenerationCapacity / us-gaap_BusinessAcquisitionAxis = cpn_BroadRiverEnergyCenterMemberDomain
Proceeds from Sale of Productive Assets		423us-gaap_ProceedsFromSaleOfProductiveAssets / us-gaap_BusinessAcquisitionAxis = cpn_BroadRiverEnergyCenterMemberDomain
Gain (Loss) on Disposition of Assets		215us-gaap_GainLossOnDispositionOfAssets / us-gaap_BusinessAcquisitionAxis = cpn_BroadRiverEnergyCenterMemberDomain
Ownership percentage before divestiture of business				100.00%cpn_OwnershipPercentageBeforeDivestitureOfBusiness / us-gaap_BusinessAcquisitionAxis = cpn_BroadRiverEnergyCenterMemberDomain
Incremental CCFC Term Loans [Member]
Business Acquisition [Line Items]
Debt Instrument, Face Amount	425us-gaap_DebtInstrumentFaceAmount / us-gaap_LongtermDebtTypeAxis = cpn_IncrementalCCFCTermLoansMember
Six Power Plants [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Productive Assets	1,570us-gaap_ProceedsFromSaleOfProductiveAssets / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
Number of power plants disposed of	6
Ownership percentage before divestiture of business					100.00%cpn_OwnershipPercentageBeforeDivestitureOfBusiness / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
Working Capital Adjustment to Sale price	2cpn_WorkingCapitalAdjustmenttoSaleprice / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
Cost of Property Repairs and Maintenance	12us-gaap_CostOfPropertyRepairsAndMaintenance / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
Business Combination, Contingent Consideration, Liability	4us-gaap_BusinessCombinationContingentConsiderationLiability / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
(Gain) on sale of power plants, net	$ 753us-gaap_GainLossOnDispositionOfAssets1 / us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis = cpn_SixPowerPlantsMember
Oneta Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						1,134cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_OnetaEnergyCenterMember
Carville Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						501cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_CarvilleEnergyCenterMember	[1]
Decatur Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						795cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_DecaturEnergyCenterMember
Hog Bayou Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						237cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_HogBayouEnergyCenterMember
Santa Rosa Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						225cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_SantaRosaEnergyCenterMember
Columbia Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity						606cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_ColumbiaEnergyCenterMember	[1]
Six Power Plants [Member]
Business Acquisition [Line Items]
Power generation capacity						3,498cpn_PowerGenerationCapacity / cpn_PowerPlantAxis = cpn_SixPowerPlantsMember
[1] Indicates combined-cycle cogeneration power plant.

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Working Capital Adjustment to Sale price

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Amount of liability recognized arising from contingent consideration in a business combination.

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