v2.4.1.9

Assets and Liabilities with Recurring Fair Value Measurements Fair Value Hierarchy (Details) (USD $)
In Millions, unless otherwise specified

Mar. 31, 2015

Dec. 31, 2014

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash equivalents

$ 965us-gaap_CashAndCashEquivalentsFairValueDisclosure

^[1]

$ 896us-gaap_CashAndCashEquivalentsFairValueDisclosure

^[1]

Margin deposits

107us-gaap_MarginDepositAssets

^[2]

96us-gaap_MarginDepositAssets

^[2]

Commodity futures contracts

2,037cpn_CommodityFuturesContractsAssetsFairValueDisclosure

2,134cpn_CommodityFuturesContractsAssetsFairValueDisclosure

Commodity forward contracts

528cpn_CommodityForwardContractsAssetsFairValueDisclosure

^[3]

359cpn_CommodityForwardContractsAssetsFairValueDisclosure

^[3]

Interest Rate Swap Assets, Fair Value Disclosure

4cpn_InterestRateSwapAssetsFairValueDisclosure

4cpn_InterestRateSwapAssetsFairValueDisclosure

Total assets

3,641us-gaap_AssetsFairValueDisclosure

3,489us-gaap_AssetsFairValueDisclosure

Margin deposits held by us posted by our counterparties

40us-gaap_SecurityDepositLiability

^[2],[4]

47us-gaap_SecurityDepositLiability

^[2],[4]

Commodity futures contracts

1,814cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure

1,870cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure

Commodity forward contracts

283cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure

^[3]

242cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure

^[3]

Interest rate swaps

118cpn_InterestRateSwapLiabilitiesFairValueDisclosure

114cpn_InterestRateSwapLiabilitiesFairValueDisclosure

Liabilities, Fair Value Disclosure

2,255us-gaap_LiabilitiesFairValueDisclosure

2,273us-gaap_LiabilitiesFairValueDisclosure

Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash equivalents

965us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[1]

896us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[1]

Margin deposits

107us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

96us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Commodity futures contracts

2,037cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

2,134cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Commodity forward contracts

0cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[3]

0cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[3]

Interest Rate Swap Assets, Fair Value Disclosure

0cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

0cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Total assets

3,109us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

3,126us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Margin deposits held by us posted by our counterparties

40us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

47us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Commodity futures contracts

1,814cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

1,870cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Commodity forward contracts

0cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[3]

0cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

^[3]

Interest rate swaps

0cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

0cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Liabilities, Fair Value Disclosure

1,854us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

1,917us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member

Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash equivalents

0us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[1]

0us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[1]

Margin deposits

0us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

0us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Commodity futures contracts

0cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

0cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Commodity forward contracts

295cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[3]

195cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[3]

Interest Rate Swap Assets, Fair Value Disclosure

4cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

4cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Total assets

299us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

199us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Margin deposits held by us posted by our counterparties

0us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

0us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Commodity futures contracts

0cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

0cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Commodity forward contracts

253cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[3]

163cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

^[3]

Interest rate swaps

118cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

114cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Liabilities, Fair Value Disclosure

371us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

277us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member

Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Cash equivalents

0us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[1]

0us-gaap_CashAndCashEquivalentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[1]

Margin deposits

0us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0us-gaap_MarginDepositAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Commodity futures contracts

0cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0cpn_CommodityFuturesContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Commodity forward contracts

233cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[3]

164cpn_CommodityForwardContractsAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[3]

Interest Rate Swap Assets, Fair Value Disclosure

0cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0cpn_InterestRateSwapAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Total assets

233us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

164us-gaap_AssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Margin deposits held by us posted by our counterparties

0us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0us-gaap_SecurityDepositLiability
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Commodity futures contracts

0cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0cpn_CommodityFuturesContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Commodity forward contracts

30cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[3]

79cpn_CommodityForwardContractsLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

^[3]

Interest rate swaps

0cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

0cpn_InterestRateSwapLiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

Liabilities, Fair Value Disclosure

$ 30us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

$ 79us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member

[1]	As of March 31, 2015 and December 31, 2014, we had cash equivalents of $757 million and $679 million included in cash and cash equivalents and $208 million and $217 million included in restricted cash, respectively.
[2]	Balances are subject to master netting arrangements and presented on a gross basis on our Consolidated Condensed Balance Sheets. We do not offset fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement for financial statement presentation, and we do not offset amounts recognized for the right to reclaim, or the obligation to return, cash collateral with corresponding derivative instrument fair values. See Note 5 for further discussion of our derivative instruments subject to master netting arrangements.
[3]	Includes OTC swaps and options.
[4]	Included in other current liabilities on our Consolidated Condensed Balance Sheets.

X

- Definition

Commodity Forward Contracts Assets, Fair Value Disclosure

+ References

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- Definition

Commodity Forward Contracts Liabilities, Fair Value Disclosure

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Commodity Futures Contracts Assets, Fair Value Disclosure

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Commodity Futures Contracts Liabilities, Fair Value Disclosure

+ References

No definition available.

+ Details

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Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
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X

- Definition

Interest Rate Swap Assets, Fair Value Disclosure

+ References

No definition available.

+ Details

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- Definition

Interest Rate Swap Liabilities, Fair Value Disclosure

+ References

No definition available.

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X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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X

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951



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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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- Definition

Fair value of financial and nonfinancial obligations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8,17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

This element represents money paid in advance to protect the provider of a product or service, such as a lessor, against damage or nonpayment by the buyer or tenant (lessee) during the term of the agreement. Such damages may include physical damage to the property, theft of property, and other contractual breaches. Security deposits held may be interest or noninterest bearing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.15(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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