v2.4.0.6

Variable Interest Entities and Unconsolidated Investments (VIE Textuals) (Details) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2012 USD ($) MW	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($) MW	Sep. 30, 2011 USD ($)	Dec. 31, 2011 USD ($) MW	Sep. 30, 2012 Greenfield [Member] USD ($)	Sep. 30, 2011 Greenfield [Member] USD ($)	Sep. 30, 2012 Greenfield [Member] USD ($)	Sep. 30, 2011 Greenfield [Member] USD ($)	Sep. 30, 2012 Greenfield [Member] CAD MW	Sep. 30, 2012 Whitby [Member] USD ($) MW	Sep. 30, 2011 Whitby [Member] USD ($)	Sep. 30, 2012 Whitby [Member] USD ($) MW	Sep. 30, 2011 Whitby [Member] USD ($)	Sep. 30, 2012 Inland Empire Energy Center [Member] Y MW	Sep. 30, 2012 Inland Empire Energy Center [Member] Maximum [Member] Y	Sep. 30, 2012 Inland Empire Energy Center [Member] Minimum [Member] Y
Variable Interest Entity [Line Items]
Power generation capacity	10,500		10,500		11,391					1,038	50		50		775
Variable Interest Entity, Financial or Other Support, Amount	$ 0	$ 15	$ 0	$ 87
Equity Method Investment, Ownership Percentage										50.00%	50.00%		50.00%
Equity Method Investment, Summarized Financial Information, Debt	460		460		462
Prorata Share of Equity Method Investment, Summarized Financial Information, Debt	230		230		231
Equity Method Investment, Summarized Financial Information, Term Loan Period										18 years
Equity Method Investment, Summarized Financial Information, Term Loan										648
Project financing interest rate spread - Canadian LIBOR										1.125%
Project financing interest rate spread - Canadian Prime Rate										0.125%
Distribution from equity method investee						$ 9	$ 0	$ 18	$ 2		$ 0	$ 0	$ 7	$ 4
Call Option Exercise Period																2,024	2,017
Put Option Exercise Period															2,025

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

Distribution from equity method investee

+ References

No definition available.

+ Details

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

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:	na
Period Type:	instant

X

- Definition

Equity Method Investment, Summarized Financial Information, Term Loan

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationTermLoan
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Equity Method Investment, Summarized Financial Information, Term Loan Period

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationTermLoanPeriod
Namespace Prefix:	cpn_
Data Type:	xbrli:durationItemType
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

Project financing interest rate spread - Canadian LIBOR

+ References

No definition available.

+ Details

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

X

- Definition

Project financing interest rate spread - Canadian Prime Rate

+ References

No definition available.

+ Details

Name:	cpn_ProjectFinancingInterestRateSpreadCanadianPrimeRate
Namespace Prefix:	cpn_
Data Type:	num:percentItemType
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:	na
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 Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: 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



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

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=7880789&loc=SL6759159-111685



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)-8

-Paragraph C4

-Subparagraph c

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

X

- Details

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