Debt (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended													9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011 Corporate Revolving Facility		Dec. 31, 2010 Corporate Revolving Facility		Sep. 30, 2011 Calpine Development Holdings, Inc.	Dec. 31, 2010 Calpine Development Holdings, Inc.	Sep. 30, 2011 NDH Project Debt credit facility		Dec. 31, 2010 NDH Project Debt credit facility		Sep. 30, 2011 Various project financing facilities	Dec. 31, 2010 Various project financing facilities	Sep. 30, 2011 Minimum	Sep. 30, 2011 Maximum	Sep. 30, 2011 One Month	Sep. 30, 2011 Two Months	Sep. 30, 2011 Three Months	Sep. 30, 2011 Six Months	Sep. 30, 2011 Nine Months	Sep. 30, 2011 Twelve Months
Amounts issued under letter of credit facilities [Line Items]
Fair value of amounts outstanding		$ 402	[1]	$ 443	[1]	$ 163	$ 165		[2]	$ 34	[2]	$ 130	$ 69
Corporate Revolving Facility Interest Details [Abstract]
Applicable margin range percentage above base rate														2.00%	2.25%
Percentage added to Federal Funds Effective Rate to arrive at base rate	0.50%
Interest periods for LIBOR rate borrowings																1	2	3	6	9	12
Applicable margin range percentage added to the British Bankers' Association Interest Settlement Rates														3.00%	3.25%
Unused commitment fee range percentage														0.50%	0.75%

[1] When we entered into our $1.0 billion Corporate Revolving Facility on December 10, 2010, the letters of credit issued under our First Lien Credit Facility were either replaced with letters of credit issued by our Corporate Revolving Facility or back-stopped by an irrevocable standby letter of credit issued by a third party. Our letters of credit under our Corporate Revolving Facility at December 31, 2010 include those that were back-stopped of approximately $83 million. The back-stopped letters of credit were returned and extinguished during the first quarter of 2011.

[2] We repaid and terminated the NDH Project Debt on March 9, 2011.