v2.4.0.6

Acquisitions and Divestitures Acquisition of Bosque (Details) (USD $) In Millions, unless otherwise specified | Sep. 30, 2012 MW | Dec. 31, 2011 MW
--- | --- | ---
Business Acquisition [Line Items] |  |
Power generation capacity | 10,500 | 11,391
Bosque Energy Center [Member] |  |
Business Acquisition [Line Items] |  |
Business Acquisition, Purchase Price Allocation, Assets Acquired | 432 |
Power generation capacity | 800 |
Block one power generation capacity | 250 |
Block two power generation capacity | 550 |

X
- Definition Block one power generation capacity + References No definition available. + Details
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Namespace Prefix: | cpn_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Block two power generation capacity + References No definition available. + Details
Name: | cpn_BlockTwoPowerGenerationCapacity
Namespace Prefix: | cpn_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Power generation capacity + References No definition available. + Details
Name: | cpn_PowerGenerationCapacity
Namespace Prefix: | cpn_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of acquisition cost of a business combination allocated to assets acquired. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 141 -Paragraph 37 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant