v2.4.1.9

Commitments and Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies [Line Items]
Guarantor Obligations, Current Carrying Value	$ 2us-gaap_GuaranteeObligationsCurrentCarryingValue
Outstanding claims related to guarantees	0cpn_OutstandingClaimsRelatedToGuarantees
Royalty Expense	28us-gaap_RoyaltyExpense	27us-gaap_RoyaltyExpense	22us-gaap_RoyaltyExpense
LTSA [Member]
Unrecorded Unconditional Purchase Obligation
Unrecorded Unconditional Purchase Obligation	189us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount / us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis = cpn_LtsaMember
Term of Unrecorded Unconditional Purchase Obligation Lower Limit	1 year
Term of Unrecorded Unconditional Purchase Obligation Upper Limit	11 years
Electric Generation Equipment [Member]
Commitments and Contingencies [Line Items]
Operating Leases, Rent Expense, Net	46us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember	47us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember	51us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_ElectricGenerationEquipmentMember
Office Equipment [Member]
Commitments and Contingencies [Line Items]
Operating Leases, Rent Expense, Net	$ 11us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember	$ 12us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember	$ 12us-gaap_OperatingLeasesRentExpenseNet / cpn_OperatingLeaseAssetsAxis = us-gaap_OfficeEquipmentMember

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- Definition

Outstanding claims related to guarantees

+ References

No definition available.

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- Definition

Term of Unrecorded Unconditional Purchase Obligation Lower Limit

+ References

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- Definition

Term of Unrecorded Unconditional Purchase Obligation Upper Limit

+ References

No definition available.

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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

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- Definition

Amount of expense related to royalty payments under a contractual arrangement such as payment for mineral and drilling rights and use of technology or intellectual property.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

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