Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 MMBTU MW		Dec. 31, 2011 MW MMBTU
Derivative Instruments [Abstract]
Nonmonetary Notional Amount of Price Risk Derivatives Power	(16)		(21)
Price Risk Derivatives [Abstract]
Natural gas (MMBtu)	66		(200)
Interest rate swaps	$ 1,602	[1]	$ 5,639	[1]

[1] Approximately $4.1 billion at December 31, 2011 was related to hedges of our First Lien Credit Facility’s variable rate debt that was converted to fixed rate debt. On March 26, 2012, we terminated the interest rate swaps formerly hedging our First Lien Credit Facility