Acquisitions and Divestitures	9 Months Ended
Sep. 30, 2012
Business Combinations [Abstract]
Acquisitions and Divestitures	Acquisition and Divestitures Calpine Bosque Energy Center On October 3, 2012, we, through our indirect, wholly owned subsidiary Calpine Bosque Energy Center, LLC, agreed to purchase a power plant with a nameplate capacity of 800 MW owned by Bosque Power Co., LLC, for approximately $432 million. The natural gas-fired, combined-cycle power plant will increase capacity in our Texas segment and is located in Central Texas near the unincorporated community of Laguna Park in Bosque County. The site includes a 250 MW generation block with one natural-gas turbine, one heat recovery steam generator and one steam turbine that achieved COD in June 2001 and a 550 MW generation block with two natural-gas turbines that went online in June 2000 as well as two heat recovery steam generators and one steam turbine that achieved COD in June 2011. We expect the transaction to close in November 2012, subject to regulatory approvals, and will fund the acquisition with cash on hand. Riverside Energy Center Our 603 MW Riverside Energy Center has a PPA that provides WP&L an option to purchase the power plant and plant-related assets for approximately $392 million upon written notice of exercise prior to May 31, 2012. On May 18, 2012, WP&L exercised their option to purchase Riverside Energy Center, LLC, one of our VIEs which owns Riverside Energy Center. The sale is expected to close in December 2012. The assets being disposed of did not meet the criteria for classification as held for sale under U.S. GAAP, and we do not expect a material gain (loss) on sale. At September 30, 2012, Riverside Energy Center, LLC had total assets of $436 million and total liabilities of $1 million, which includes working capital of approximately $42 million that will not be included in the sale. Broad River Energy Center On November 1, 2012, we, through our indirect, wholly owned subsidiary Calpine Power Company, entered into an agreement with Broad River Power to sell 100% of our ownership interests in each of the Broad River Entities for approximately $427 million, including a five year consulting agreement and subject to certain working capital adjustments at closing. Under the agreement, Calpine Power Company will use commercially reasonable efforts to cause Broad River Energy Center to continue to operate and maintain the power plant in the ordinary course of business through the closing of the transaction, which is expected to occur in December 2012, subject to regulatory approvals. We expect to use the sale proceeds to focus more resources on our core markets and for general corporate purposes.

Acquisition and Divestitures

Calpine Bosque Energy Center

On October 3, 2012, we, through our indirect, wholly owned subsidiary Calpine Bosque Energy Center, LLC, agreed to purchase a power plant with a nameplate capacity of 800 MW owned by Bosque Power Co., LLC, for approximately $432 million. The natural gas-fired, combined-cycle power plant will increase capacity in our Texas segment and is located in Central Texas near the unincorporated community of Laguna Park in Bosque County. The site includes a 250 MW generation block with one natural-gas turbine, one heat recovery steam generator and one steam turbine that achieved COD in June 2001 and a 550 MW generation block with two natural-gas turbines that went online in June 2000 as well as two heat recovery steam generators and one steam turbine that achieved COD in June 2011. We expect the transaction to close in November 2012, subject to regulatory approvals, and will fund the acquisition with cash on hand.

Riverside Energy Center

Our 603 MW Riverside Energy Center has a PPA that provides WP&L an option to purchase the power plant and plant-related assets for approximately $392 million upon written notice of exercise prior to May 31, 2012. On May 18, 2012, WP&L exercised their option to purchase Riverside Energy Center, LLC, one of our VIEs which owns Riverside Energy Center. The sale is expected to close in December 2012. The assets being disposed of did not meet the criteria for classification as held for sale under U.S. GAAP, and we do not expect a material gain (loss) on sale. At September 30, 2012, Riverside Energy Center, LLC had total assets of $436 million and total liabilities of $1 million, which includes working capital of approximately $42 million that will not be included in the sale.

Broad River Energy Center

On November 1, 2012, we, through our indirect, wholly owned subsidiary Calpine Power Company, entered into an agreement with Broad River Power to sell 100% of our ownership interests in each of the Broad River Entities for approximately $427 million, including a five year consulting agreement and subject to certain working capital adjustments at closing. Under the agreement, Calpine Power Company will use commercially reasonable efforts to cause Broad River Energy Center to continue to operate and maintain the power plant in the ordinary course of business through the closing of the transaction, which is expected to occur in December 2012, subject to regulatory approvals. We expect to use the sale proceeds to focus more resources on our core markets and for general corporate purposes.