Debt (Project Financing, Notes Payable and Others) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Long-term Debt	$ 10,750		$ 10,425
Steamboat [Member]
Debt Instrument [Line Items]
Long-term Debt	507		244
Debt Instrument, Interest Rate, Effective Percentage	3.60%	[1]	4.10%	[1]
OMEC [Member]
Debt Instrument [Line Items]
Long-term Debt	428		437
Debt Instrument, Interest Rate, Effective Percentage	6.80%	[1]	6.60%	[1]
Russell City Project [Member]
Debt Instrument [Line Items]
Long-term Debt	345		355
Debt Instrument, Interest Rate, Effective Percentage	6.80%	[1]	6.80%	[1]
BRSP [Member]
Debt Instrument [Line Items]
Long-term Debt	209		83
Debt Instrument, Interest Rate, Effective Percentage	3.50%	[1]	3.80%	[1]
Pasadena [Member]
Debt Instrument [Line Items]
Long-term Debt	160	[2]	185	[2]
Debt Instrument, Interest Rate, Effective Percentage	8.90%	[1],[2]	8.80%	[1],[2]
Bethpage [Member]
Debt Instrument [Line Items]
Long-term Debt	93	[3]	98	[3]
Debt Instrument, Interest Rate, Effective Percentage	7.00%	[1],[3]	7.00%	[1],[3]
Los Esteros Project [Member]
Debt Instrument [Line Items]
Long-term Debt	33		49
Debt Instrument, Interest Rate, Effective Percentage	10.80%	[1]	10.60%	[1]
Gilroy note payable [Member]
Debt Instrument [Line Items]
Long-term Debt	0	[4]	232	[4]
Debt Instrument, Interest Rate, Effective Percentage	0.00%	[1],[4]	5.70%	[1],[4]
Other Credit Derivatives [Member]
Debt Instrument [Line Items]
Long-term Debt	14		8
Debt Instrument, Interest Rate, Effective Percentage	0.00%	[1]	0.00%	[1]
Project Financing Total [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 1,789		$ 1,691

[1] Our weighted average interest rate calculation includes the amortization of deferred financing costs and debt discount or premium.

[2] Represents a sale-leaseback transaction that is accounted for as financing transaction under U.S. GAAP.

[3] Represents a weighted average of first and second lien loans for the weighted average effective interest rates.

[4] During the fourth quarter of 2012, we repaid the Calpine BRSP project debt with proceeds received from the issuance of our 2019 First Lien Term Loan.