v2.4.1.9

Commitments and Contingencies (Schedules of Future Minimum Rental Payments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Land and Other Operating Leases [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	$ 277us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments Due, Current	15us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments, Due in Two Years	16us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments, Due in Three Years	15us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments, Due in Four Years	15us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments, Due in Five Years	15us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Operating Leases, Future Minimum Payments, Due Thereafter	201us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cpn_OperatingLeaseAssetsAxis = cpn_LandAndOtherOperatingLeasesMember
Greenleaf [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	4us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = cpn_GreenleafMember
KIAC [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	119us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments Due, Current	23us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments, Due in Two Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments, Due in Three Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments, Due in Four Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments, Due in Five Years	30us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Operating Leases, Future Minimum Payments, Due Thereafter	0us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cpn_OperatingLeaseAssetsAxis = cpn_KiacMember
Total Power Plant Leases [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	123us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments Due, Current	27us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments, Due in Two Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments, Due in Three Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments, Due in Four Years	22us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments, Due in Five Years	30us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operating Leases, Future Minimum Payments, Due Thereafter	0us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Operting Lease Assets Total [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	400us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments Due, Current	42us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments, Due in Two Years	38us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments, Due in Three Years	37us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments, Due in Four Years	37us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments, Due in Five Years	45us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Operating Leases, Future Minimum Payments, Due Thereafter	201us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cpn_OperatingLeaseAssetsAxis = cpn_OpertingLeaseAssetsTotalMember
Office Equipment [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	55us-gaap_OperatingLeasesFutureMinimumPaymentsDue / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments Due, Current	11us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments, Due in Two Years	10us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments, Due in Three Years	9us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments, Due in Four Years	9us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments, Due in Five Years	8us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Operating Leases, Future Minimum Payments, Due Thereafter	8us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember
Greenleaf [Member]
Operating Leased Assets [Line Items]
Guarantee Obligations Balance On First Anniversary	4cpn_GuaranteeObligationsBalanceOnFirstAnniversary / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Guarantee Obligations Balance On Second Anniversary	0cpn_GuaranteeObligationsBalanceOnSecondAnniversary / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Guarantee Obligations Balance On Third Anniversary	0cpn_GuaranteeObligationsBalanceOnThirdAnniversary / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Guarantee Obligations Balance On Fourth Anniversary	0cpn_GuaranteeObligationsBalanceOnFourthAnniversary / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Guarantee Obligations Balance On Fifth Anniversary	0cpn_GuaranteeObligationsBalanceOnFifthAnniversary / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Guarantee Obligations Due After Five Years	0cpn_GuaranteeObligationsDueAfterFiveYears / us-gaap_GuaranteeObligationsByNatureAxis = cpn_GreenleafMember	[1]
Natural Gas [Member]
Operating Leased Assets [Line Items]
Operating Leases, Future Minimum Payments Due	1,763us-gaap_OperatingLeasesFutureMinimumPaymentsDue / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments Due, Current	390us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments, Due in Two Years	297us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments, Due in Three Years	193us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments, Due in Four Years	152us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments, Due in Five Years	109us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
Operating Leases, Future Minimum Payments, Due Thereafter	$ 622us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / us-gaap_ProductOrServiceAxis = us-gaap_NaturalGasReservesMember
[1] These are contingent off balance sheet obligations.

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- Definition

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717



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- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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