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

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Data Type:	xbrli:stringItemType
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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

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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

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