v2.4.1.9

Variable Interest Entities and Unconsolidated Investments (VIE Textuals) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 MW	Dec. 31, 2013 MW	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Power generation capacity	10,365cpn_PowerGenerationCapacity	9,427cpn_PowerGenerationCapacity
Variable Interest Entity, Financial or Other Support, Amount	$ 47,000,000us-gaap_VariableInterestEntityFinancialOrOtherSupportAmount	$ 0us-gaap_VariableInterestEntityFinancialOrOtherSupportAmount	$ 20,000,000us-gaap_VariableInterestEntityFinancialOrOtherSupportAmount
Equity Method Investment, Summarized Financial Information, Debt	342,000,000cpn_EquityMethodInvestmentSummarizedFinancialInformationDebt	395,000,000cpn_EquityMethodInvestmentSummarizedFinancialInformationDebt
Prorata Share of Equity Method Investment, Summarized Financial Information, Debt	$ 171,000,000cpn_ProrataShareOfEquityMethodInvestmentSummarizedFinancialInformationDebt	$ 198,000,000cpn_ProrataShareOfEquityMethodInvestmentSummarizedFinancialInformationDebt
Russell City Energy [Member]
Schedule of Equity Method Investments [Line Items]
Minority Interest Ownership Percentage By Noncontrolling Third Party Owners	25.00%cpn_MinorityInterestOwnershipPercentageByNoncontrollingThirdPartyOwners / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_RussellCityEnergyMember
Equity Method Investment, Ownership Percentage	75.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_RussellCityEnergyMember
Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity	775cpn_PowerGenerationCapacity / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_InlandEmpireEnergyCenterMember
Put Option Exercise Period	2,025cpn_PutOptionExercisePeriod / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_InlandEmpireEnergyCenterMember
Minimum [Member] | Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Call Option Exercise Period	2,017cpn_CallOptionExercisePeriod / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_InlandEmpireEnergyCenterMember
Maximum [Member] | Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Call Option Exercise Period	2,024cpn_CallOptionExercisePeriod / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis = cpn_InlandEmpireEnergyCenterMember
Greenfield [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity	1,038cpn_PowerGenerationCapacity / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_GreenfieldMember
Equity Method Investment, Ownership Percentage	50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_GreenfieldMember
Whitby [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity	50cpn_PowerGenerationCapacity / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_WhitbyMember
Equity Method Investment, Ownership Percentage	50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cpn_WhitbyMember

X

- Definition

Call Option Exercise Period

+ References

No definition available.

+ Details

Name:	cpn_CallOptionExercisePeriod
Namespace Prefix:	cpn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Equity Method Investment, Summarized Financial Information, Debt

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationDebt
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Minority Interest Ownership Percentage By Noncontrolling Third Party Owners

+ References

No definition available.

+ Details

Name:	cpn_MinorityInterestOwnershipPercentageByNoncontrollingThirdPartyOwners
Namespace Prefix:	cpn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Power generation capacity

+ References

No definition available.

+ Details

Name:	cpn_PowerGenerationCapacity
Namespace Prefix:	cpn_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Prorata Share of Equity Method Investment, Summarized Financial Information, Debt

+ References

No definition available.

+ Details

Name:	cpn_ProrataShareOfEquityMethodInvestmentSummarizedFinancialInformationDebt
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Put Option Exercise Period

+ References

No definition available.

+ Details

Name:	cpn_PutOptionExercisePeriod
Namespace Prefix:	cpn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of financial or other support the reporting entity has provided (explicitly or implicitly) to the Variable Interest Entity (VIE) that it was not previously contractually required to provide or that the reporting entity intends to provide, including, for example, situations in which the reporting entity assisted the VIE in obtaining another type of support.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=SL6759159-111685

+ Details

Name:	us-gaap_VariableInterestEntityFinancialOrOtherSupportAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=cpn_GreenfieldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=cpn_WhitbyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=cpn_InlandEmpireEnergyCenterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=cpn_RussellCityEnergyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: