v2.4.0.8

Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2013 MWh MMBTU | Dec. 31, 2012 MWh MMBTU
Derivative Instruments [Abstract] |  |
Derivative, Nonmonetary Notional Amount, Energy Measure | (11) | (16)
Nonmonetary Notional Amount of Price Risk Derivatives Natural Gas | 163 | 66
Price Risk Derivatives [Abstract] |  |
Derivative, Notional Amount | $ 1,597 | $ 1,602

X
- Details
Name: | cpn_DerivativeInstrumentsAbstract
Namespace Prefix: | cpn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nonmonetary Notional Amount of Price Risk Derivatives Natural Gas + References No definition available. + Details
Name: | cpn_NonmonetaryNotionalAmountOfPriceRiskDerivativesNaturalGas
Namespace Prefix: | cpn_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | instant

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix: | us-gaap_
Data Type: | num:energyItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PriceRiskDerivativesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration