v2.4.1.9

Derivative Instruments (Details 3) (Details) (USD $)
In Millions, unless otherwise specified

3 Months Ended

12 Months Ended

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) on Sale of Derivatives

$ 110us-gaap_GainLossOnSaleOfDerivatives

^[1]

$ 86us-gaap_GainLossOnSaleOfDerivatives

^[1]

$ 230us-gaap_GainLossOnSaleOfDerivatives

^[1]

Unrealized Gain (Loss) on Derivatives

353us-gaap_UnrealizedGainLossOnDerivatives

^[2]

(12)us-gaap_UnrealizedGainLossOnDerivatives

^[2]

72us-gaap_UnrealizedGainLossOnDerivatives

^[2]

Derivatives contracts included in operating revenues

1,939us-gaap_Revenues

2,187us-gaap_Revenues

1,939us-gaap_Revenues

1,965us-gaap_Revenues

1,438us-gaap_Revenues

2,050us-gaap_Revenues

1,572us-gaap_Revenues

1,241us-gaap_Revenues

8,030us-gaap_Revenues

6,301us-gaap_Revenues

5,478us-gaap_Revenues

Derivatives contracts included in fuel and purchased energy

4,892us-gaap_CostOfRevenue

3,736us-gaap_CostOfRevenue

3,024us-gaap_CostOfRevenue

Interest expense

645us-gaap_InterestExpense

696us-gaap_InterestExpense

736us-gaap_InterestExpense

Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments

0us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments

0us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments

(14)us-gaap_GainLossOnInterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstruments

Gain (Loss) on Derivative Instruments, Net, Pretax

463us-gaap_GainLossOnDerivativeInstrumentsNetPretax

74us-gaap_GainLossOnDerivativeInstrumentsNetPretax

302us-gaap_GainLossOnDerivativeInstrumentsNetPretax

Energy Related Derivative [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) on Sale of Derivatives

110us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[1]

86us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[1]

387us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[1]

Unrealized Gain (Loss) on Derivatives

342us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[2]

(14)us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[2]

(82)us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_EnergyRelatedDerivativeMember

^[2]

Interest Rate Swap [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) on Sale of Derivatives

0us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[1]

0us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[1]

(157)us-gaap_GainLossOnSaleOfDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[1]

Unrealized Gain (Loss) on Derivatives

11us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[2]

2us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[2]

154us-gaap_UnrealizedGainLossOnDerivatives
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

^[2]

Interest expense

11us-gaap_InterestExpense
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

2us-gaap_InterestExpense
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

11us-gaap_InterestExpense
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember

Power [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Derivatives contracts included in operating revenues

384us-gaap_Revenues
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_PowerMember

(119)us-gaap_Revenues
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_PowerMember

187us-gaap_Revenues
/ us-gaap_DerivativeInstrumentRiskAxis
= cpn_PowerMember

Natural Gas [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Derivatives contracts included in fuel and purchased energy

$ 68us-gaap_CostOfRevenue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_NaturalGasReservesMember

$ 191us-gaap_CostOfRevenue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_NaturalGasReservesMember

$ 118us-gaap_CostOfRevenue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_NaturalGasReservesMember

[1]	Does not include the realized value associated with derivative instruments that settle through physical delivery.
[2]	In addition to changes in market value on derivatives not designated as hedges, changes in mark-to-market gain (loss) also includes de-designation of interest rate swap cash flow hedges and related reclassification from AOCI into earnings, hedge ineffectiveness and adjustments to reflect changes in credit default risk exposure.

X

- Definition

The aggregate cost of goods produced and sold and services rendered during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 2

-Article 5

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X

- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of gain (loss) included in earnings for the period from the increase (decrease) in fair value of interest rate derivatives not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

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X

- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(h))

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X

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.9)

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 9

-Article 9

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X

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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X

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EnergyRelatedDerivativeMember
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X

- Details

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X

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