Variable Interest Entities and Unconsolidated Investments (Equity Method Investment Summarized Financial Information) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Method Investment, Summarized Financial Information, Assets [Abstract]
Equity Method Investment Summarized Financial Information Cash and Cash Equivalents	$ 58	$ 57
Equity Method Investment, Summarized Financial Information, Current Assets	28	25
Equity Method Investment, Summarized Financial Information, Property, Plant and Equipment, net	532	588
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	2	2
Equity Method Investment, Summarized Financial Information, Assets	620	672
Equity Method Investment, Summarized Financial Information, Liabilities [Abstract]
Equity Method Investment, Summarized Financial Information, Current Maturities of Long-term Debt	21	23
Equity Method Investment, Summarized Financial Information, Current Liabilities	28	44
Equity Method Investment, Summarized Financial Information, Long-Term Debt	321	372
Equity Method Investment, Summarized Financial Information, Long-term Derivative Liabilities	51	35
Equity Method Investment, Summarized Financial Information, Liabilities	421	474
Equity Method Investment Summarized Financial Information, Equity [Abstract]
Equity Method Investment Summarized Financial Information, Equity	199	198
Equity Method Investment, Summarized Financial Information, Liabilities and Equity	620	672
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) [Abstract]
Equity Method Investment, Summarized Financial Information, Revenue	239	207	247
Equity Method Investment, Summarized Financial Information, Cost of Sales	168	128	171
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)	71	79	76
Equity Method Investment Summarized Financial Information Interest (Income) Expense	23	24	27
Equity Method Investment Summarized Financial Information Other (Income) Expense Net	0	(3)	(2)
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$ 48	$ 58	$ 51

Equity Method Investment Summarized Financial Information Cash and Cash Equivalents

No definition available.

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationCashAndCashEquivalents
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Equity Method Investment, Summarized Financial Information, Current Maturities of Long-term Debt

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationCurrentMaturitiesOfLongTermDebt
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Equity Method Investment Summarized Financial Information Interest (Income) Expense

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationInterestIncomeExpense
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Equity Method Investment, Summarized Financial Information, Long-Term Debt

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationLongTermDebt
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Equity Method Investment, Summarized Financial Information, Long-term Derivative Liabilities

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationLongTermDerivativeLiabilities
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Equity Method Investment Summarized Financial Information Other (Income) Expense Net

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationOtherIncomeExpenseNet
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Equity Method Investment, Summarized Financial Information, Property, Plant and Equipment, net

+ References

No definition available.

+ Details

Name:	cpn_EquityMethodInvestmentSummarizedFinancialInformationPropertyPlantAndEquipmentNet
Namespace Prefix:	cpn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of assets reported by an equity method investment of the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(g))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph bb

-Article 1

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph g

-Subparagraph 1, 2

-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph w

-Article 1

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssetsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost of sales reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCostOfSales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of current assets reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current liabilities reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of equity, including noncontrolling interest, reported by an equity method investment of the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.g)

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationEquityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of gross profit (loss) reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLossAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of liabilities and equity reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilitiesAndEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of net income (loss) reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of noncurrent assets reported by an equity method investment of the entity.

+ References

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

Name:	us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration