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Commitments and Contingencies (Schedule of Guarantor Obligations) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012
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Loans Payable [Member] |  |
Guarantor Obligations [Line Items] |  |
Guarantee Obligations Balance On First Anniversary | $ 47 | [1]
Guarantee Obligations Balance On Second Anniversary | 36 | [1]
Guarantee Obligations Balance On Third Anniversary | 37 | [1]
Guarantee Obligations Balance On Fourth Anniversary | 36 | [1]
Guarantee Obligations Balance On Fifth Anniversary | 26 | [1]
Guarantee Obligations Due After Five Years | 209 | [1]
Guarantor Obligations, Maximum Exposure, Undiscounted | 391 | [1]
Financial Standby Letter of Credit [Member] |  |
Guarantor Obligations [Line Items] |  |
Guarantee Obligations Balance On First Anniversary | 536 | [2],[3]
Guarantee Obligations Balance On Second Anniversary | 41 | [2],[3]
Guarantee Obligations Balance On Third Anniversary | 0 | [2],[3]
Guarantee Obligations Balance On Fourth Anniversary | 0 | [2],[3]
Guarantee Obligations Balance On Fifth Anniversary | 19 | [2],[3]
Guarantee Obligations Due After Five Years | 30 | [2],[3]
Guarantor Obligations, Maximum Exposure, Undiscounted | 626 | [2],[3]
Surety Bonds [Member] |  |
Guarantor Obligations [Line Items] |  |
Guarantee Obligations Balance On First Anniversary | 0 | [2],[4],[5]
Guarantee Obligations Balance On Second Anniversary | 0 | [2],[4],[5]
Guarantee Obligations Balance On Third Anniversary | 0 | [2],[4],[5]
Guarantee Obligations Balance On Fourth Anniversary | 0 | [2],[4],[5]
Guarantee Obligations Balance On Fifth Anniversary | 0 | [2],[4],[5]
Guarantee Obligations Due After Five Years | 4 | [2],[4],[5]
Guarantor Obligations, Maximum Exposure, Undiscounted | 4 | [2],[4],[5]
Greenleaf [Member] |  |
Guarantor Obligations [Line Items] |  |
Guarantee Obligations Balance On First Anniversary | 7 |
Guarantee Obligations Balance On Second Anniversary | 3 |
Guarantee Obligations Balance On Third Anniversary | 0 |
Guarantee Obligations Balance On Fourth Anniversary | 0 |
Guarantee Obligations Balance On Fifth Anniversary | 0 |
Guarantee Obligations Due After Five Years | 0 |
Guarantor Obligations, Maximum Exposure, Undiscounted | 10 | [2]
Gurantee Obligations Total [Member] |  |
Guarantor Obligations [Line Items] |  |
Guarantee Obligations Balance On First Anniversary | 590 |
Guarantee Obligations Balance On Second Anniversary | 80 |
Guarantee Obligations Balance On Third Anniversary | 37 |
Guarantee Obligations Balance On Fourth Anniversary | 36 |
Guarantee Obligations Balance On Fifth Anniversary | 45 |
Guarantee Obligations Due After Five Years | 243 |
Guarantor Obligations, Maximum Exposure, Undiscounted | $ 1,031 |
[1] | Represents Calpine Corporation guarantees of certain power plant capital leases and related interest. All guaranteed capital leases are recorded on our Consolidated Balance Sheets.
[2] | These are contingent off balance sheet obligations.
[3] | The standby letters of credit disclosed above represent those disclosed in Note 6.
[4] | The majority of surety bonds do not have expiration or cancellation dates.
[5] | As of December 31, 2012, $3 million of cash collateral is outstanding related to these bonds.

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- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 45 -Paragraph 13 -Subparagraph b -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. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248 + Details
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