v2.4.0.8

Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014 t MWh MMBTU	Dec. 31, 2013 t MWh MMBTU
Derivative Instruments [Abstract]
Derivative, Nonmonetary Notional Amount, Energy Measure	(49)	(29)
Nonmonetary Notional Amount of Price Risk Derivatives Natural Gas	316	448
Derivative, Nonmonetary Notional Amount, Mass	2	0
Price Risk Derivatives [Abstract]
Derivative, Notional Amount	$ 1,510	$ 1,527

X

- Details

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Namespace Prefix:	cpn_
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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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

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Namespace Prefix:	us-gaap_
Data Type:	num:energyItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Nominal mass used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountMass
Namespace Prefix:	us-gaap_
Data Type:	num:massItemType
Balance Type:	na
Period Type:	duration

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- Details

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Period Type:	duration