Derivative Instruments (Details Textuals) (USD $)	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2011	Dec. 31, 2010
Derivative Instruments (Textuals) [Abstract]
Maximum length of PPAs			23
Maximum length of time hedging using commodity derivative instruments			1
Maximum length of time hedging using interest rate derivative instruments			15
Variable rate debt converted to fixed rate debt	$ 4,100,000,000		$ 4,100,000,000	$ 3,300,000,000
Fair value of derivative liabilities with credit-contingent provisions	34,000,000		34,000,000
Collateral related the fair value of derivative liabilities with credit-contingent provisions	8,000,000		8,000,000
Additional collateral required if our credit rating downgraded	10,000,000		10,000,000
Repayment amount of remaining First Lien Credit Facility term loans			1,200,000,000	3,500,000,000
2011 notional amount of interest rate swaps hedging the variable interest payments associated with the First Lien Credit Facility term loans			1,000,000
Remaining unrealized losses related to int rate swaps formerly hedging the First Lien Credit Facility	15,000,000		91,000,000
Unrealized losses associated with interest rate swap breakage costs		17,000,000	24,000,000
Cumulative cash flow hedge losses remaining in AOCI			140,000,000	122,000,000
Losses from the reclassification of interest rate contracts due to settlement	7,000,000		17,000,000
Pre-tax net gains reclassified from AOCI into net income			52,000,000
Losses from interest rate contracts reclassified from OCI into earnings			$ 15,000,000