Call Option Exercise Period

No definition available.

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

- Definition

Distribution from equity method investee

+ References

No definition available.

+ Details

Name:	cpn_DistributionFromEquityMethodInvestee
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

- 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

- 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

- 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

- 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

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

- 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

- Details

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

- Details

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

- Details

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

- Details

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

Variable Interest Entities and Unconsolidated Investments in Power Plants (VIE Texuals) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015 MW	Mar. 31, 2014	Dec. 31, 2014 MW
Variable Interest Entity [Line Items]
Power generation capacity	10,365cpn_PowerGenerationCapacity		10,365cpn_PowerGenerationCapacity
Variable Interest Entity, Financial or Other Support, Amount	$ 0		$ 40
Equity Method Investment, Summarized Financial Information, Debt	310		342
Prorata Share of Equity Method Investment, Summarized Financial Information, Debt	155		171
Greenfield [Member]
Variable Interest Entity [Line Items]
Power generation capacity	1,038
Equity Method Investment, Ownership Percentage	50.00%
Distribution from equity method investee	0	0
Whitby [Member]
Variable Interest Entity [Line Items]
Power generation capacity	50
Equity Method Investment, Ownership Percentage	50.00%
Distribution from equity method investee	$ 0	$ 13
Inland Empire Energy Center [Member]
Variable Interest Entity [Line Items]
Power generation capacity	775
Put Option Exercise Period	2,025
Inland Empire Energy Center [Member] \| Minimum [Member]
Variable Interest Entity [Line Items]
Call Option Exercise Period	2,017
Inland Empire Energy Center [Member] \| Maximum [Member]
Variable Interest Entity [Line Items]
Call Option Exercise Period	2,024