Acquisition (Notes)	9 Months Ended
Sep. 30, 2015
Business Combinations [Abstract]
Mergers, acquisitions and dispositions disclosures	Acquisitions and Divestiture Acquisition of Granite Ridge Energy Center On October 12, 2015, we, through our indirect, wholly-owned subsidiary Calpine Granite Holdings, LLC, entered into a purchase and sale agreement to acquire Granite Ridge Energy Center, a power plant with a nameplate capacity of 745 MW, from Granite Ridge Holdings, LLC, for approximately $500 million, excluding working capital adjustments. The addition of this modern, efficient, natural gas-fired, combined-cycle power plant will increase capacity in our East segment, specifically the constrained New England market. Beginning operations in 2003, Granite Ridge Energy Center is located in Londonderry, New Hampshire and features two combustion turbines, two heat recovery steam generators and one steam turbine. We expect the transaction to close in the first quarter of 2016, and expect to fund the acquisition with a combination of cash on hand and financing. Acquisition of Champion Energy On October 1, 2015, we, through our indirect, wholly-owned subsidiary Calpine Energy Services Holdco, LLC, completed the purchase of Champion Energy Marketing, LLC from a subsidiary of Crane Champion Holdco, LLC, which owned a 75% interest, and EDF Trading North America, LLC, which owned a 25% interest, for approximately $240 million, excluding working capital adjustments. Champion Energy, a leading retail electric provider, is expected to serve approximately 22 million MWh of commercial, industrial and residential customer load in 2015, concentrated in Texas, PJM and the Northeast U.S. where Calpine has a substantial power generation presence. The addition of this well-established retail sales organization is expected to provide us an important outlet for directly reaching a much greater portion of the load we serve. The purchase price was funded with cash on hand and will be primarily allocated to intangible assets, working capital accounts and derivative assets and liabilities. Any excess of the purchase price over the fair values of Champion Energy’s assets and liabilities will be recorded as goodwill; however, we do not anticipate any significant goodwill will be recognized as a result of this acquisition. We are currently evaluating the fair value of the assets acquired and liabilities assumed and will provide these disclosures in our annual report on Form 10-K for the year ended December 31, 2015. The pro forma incremental impact of Champion Energy on our results of operations for each of the three and nine months ended September 30, 2015 and 2014 is not material. Acquisition of Fore River Energy Center On November 7, 2014, we, through our indirect, wholly-owned subsidiary Calpine Fore River Energy Center, LLC, completed the purchase of our 731 MW Fore River Energy Center and related plant inventory from a subsidiary of Exelon Corporation, for approximately $530 million, excluding working capital adjustments. The purchase price allocation was finalized during the third quarter of 2015 which did not result in any material adjustments or the recognition of goodwill. Sale of Osprey Energy Center During the fourth quarter of 2014, we executed an asset sale agreement for the sale of our Osprey Energy Center to Duke Energy Florida, Inc. for approximately $166 million, excluding working capital and other adjustments. In accordance with the asset sale agreement, the sale will be consummated in January 2017 upon the conclusion of PPA with a term of 27 months. In July 2015, the transaction was approved by the FERC and the Florida Public Service Commission. This sale represents a strategic disposition of a power plant in a wholesale power market dominated by regulated utilities. The assets of Osprey Energy Center, which is in our East segment, are reported as long-term assets held for sale on our Consolidated Condensed Balance Sheet at September 30, 2015 and comprise property, plant and equipment, net.

Acquisitions and Divestiture

Acquisition of Granite Ridge Energy Center

On October 12, 2015, we, through our indirect, wholly-owned subsidiary Calpine Granite Holdings, LLC, entered into a purchase and sale agreement to acquire Granite Ridge Energy Center, a power plant with a nameplate capacity of 745 MW, from Granite Ridge Holdings, LLC, for approximately $500 million, excluding working capital adjustments. The addition of this modern, efficient, natural gas-fired, combined-cycle power plant will increase capacity in our East segment, specifically the constrained New England market. Beginning operations in 2003, Granite Ridge Energy Center is located in Londonderry, New Hampshire and features two combustion turbines, two heat recovery steam generators and one steam turbine. We expect the transaction to close in the first quarter of 2016, and expect to fund the acquisition with a combination of cash on hand and financing.

Acquisition of Champion Energy

On October 1, 2015, we, through our indirect, wholly-owned subsidiary Calpine Energy Services Holdco, LLC, completed the purchase of Champion Energy Marketing, LLC from a subsidiary of Crane Champion Holdco, LLC, which owned a 75% interest, and EDF Trading North America, LLC, which owned a 25% interest, for approximately $240 million, excluding working capital adjustments. Champion Energy, a leading retail electric provider, is expected to serve approximately 22 million MWh of commercial, industrial and residential customer load in 2015, concentrated in Texas, PJM and the Northeast U.S. where Calpine has a substantial power generation presence. The addition of this well-established retail sales organization is expected to provide us an important outlet for directly reaching a much greater portion of the load we serve. The purchase price was funded with cash on hand and will be primarily allocated to intangible assets, working capital accounts and derivative assets and liabilities. Any excess of the purchase price over the fair values of Champion Energy’s assets and liabilities will be recorded as goodwill; however, we do not anticipate any significant goodwill will be recognized as a result of this acquisition. We are currently evaluating the fair value of the assets acquired and liabilities assumed and will provide these disclosures in our annual report on Form 10-K for the year ended December 31, 2015. The pro forma incremental impact of Champion Energy on our results of operations for each of the three and nine months ended September 30, 2015 and 2014 is not material.

Acquisition of Fore River Energy Center

On November 7, 2014, we, through our indirect, wholly-owned subsidiary Calpine Fore River Energy Center, LLC, completed the purchase of our 731 MW Fore River Energy Center and related plant inventory from a subsidiary of Exelon Corporation, for approximately $530 million, excluding working capital adjustments. The purchase price allocation was finalized during the third quarter of 2015 which did not result in any material adjustments or the recognition of goodwill.

Sale of Osprey Energy Center

During the fourth quarter of 2014, we executed an asset sale agreement for the sale of our Osprey Energy Center to Duke Energy Florida, Inc. for approximately $166 million, excluding working capital and other adjustments. In accordance with the asset sale agreement, the sale will be consummated in January 2017 upon the conclusion of PPA with a term of 27 months. In July 2015, the transaction was approved by the FERC and the Florida Public Service Commission. This sale represents a strategic disposition of a power plant in a wholesale power market dominated by regulated utilities. The assets of Osprey Energy Center, which is in our East segment, are reported as long-term assets held for sale on our Consolidated Condensed Balance Sheet at September 30, 2015 and comprise property, plant and equipment, net.