Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011
Cash flows from operating activities:
Net income (loss)	$ (338)		$ (366)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization expense	299	[1]	279	[1]
Debt extinguishment costs	0		85
Deferred income taxes	(31)		(90)
(Gain) loss on sale of power plants and other, net	4		9
Unrealized mark-to-market activities, net	119	[2]	77	[2]
(Income) loss from unconsolidated investments in power projects	(14)		(7)
Return on unconsolidated investments in power plants	16		6
Stock-based compensation expense	13		12
Other	1		5
Change in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	63		(68)
Derivative instruments, net	(111)		(29)
Other assets	(122)		58
Accounts payable and accrued expenses	(86)		166
Settlement of non-hedging interest rate swaps	156		103
Other liabilities	(1)		(1)
Net cash provided by (used in) operating activities	(32)		239
Cash flows from investing activities:
Purchases of property, plant and equipment	(369)		(341)
Settlement of non-hedging interest rate swaps	(156)		(103)
(Increase) decrease in restricted cash	19		30
Purchases of deferred transmission credits	(12)		(8)
Other	5		1
Net cash used in investing activities	(513)		(421)
Cash flows from financing activities:
Repayment of Term Loans	(8)		0
Borrowings under Term Loan and New Term Loan	0		1,657
Repayments on NDH Project Debt	0		(1,283)
Issuance of First Lien Notes	0		1,200
Repayments on First Lien Credit Facility	0		(1,187)
Borrowings from project financing, notes payable and other	226		69
Repayments of project financing, notes payable and other	(46)		(419)
Capital contributions from noncontrolling interest holder	0		34
Financing costs	(5)		(67)
Stock repurchases	(290)		0
Other	3		(2)
Net cash provided by (used in) financing activities	(120)		2
Net increase (decrease) in cash and cash equivalents	(665)		(180)
Cash and cash equivalents, beginning of period	1,252		1,327
Cash and cash equivalents, end of period	587		1,147
Cash paid during the period for:
Interest, net of amounts capitalized	352		292
Income taxes	13		12
Supplemental disclosure of non-cash investing and financing activities:
Change in capital expenditures included in accounts payable	$ 3		$ 21

[1] Includes depreciation and amortization included in fuel and purchased energy expense and interest expense on our Consolidated Condensed Statements of Operations

[2] In addition to changes in market value on derivatives not designated as hedges, changes in unrealized gain (loss) also includes de-designation of interest rate swap cash flow hedges and related reclassification from AOCI into income, hedge ineffectiveness and adjustments to reflect changes in credit default risk exposure