Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Cash flows from operating activities:
Net loss	$ (195)		$ (338)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense(1)	315	[1]	299	[1]
Debt extinguishment costs	28		0
Deferred income taxes	(15)		(31)
Loss on disposition of assets	4		4
Unrealized mark-to-market activity, net	24	[2]	119	[2]
(Income) from unconsolidated investments in power plants	(16)		(14)
Return on unconsolidated investments in power plants	16		16
Stock-based compensation expense	20		13
Other	(4)		1
Change in operating assets and liabilities:
Accounts receivable	(285)		63
Derivative instruments, net	1		(111)
Other assets	(182)		(122)
Accounts payable and accrued expenses	67		(86)
Settlement of non-hedging interest rate swaps	0		156
Other liabilities	47		(1)
Net cash used in operating activities	(175)		(32)
Cash flows from investing activities:
Purchases of property, plant and equipment	(335)		(369)
Settlement of non-hedging interest rate swaps	0		(156)
Decrease in restricted cash	55		19
Purchases of deferred transmission credits	0		(12)
Other	(1)		5
Net cash used in investing activities	(281)		(513)
Cash flows from financing activities:
Repayment under First Lien Term Loans	(12)		(8)
Borrowings from CCFC Term Loans	1,197		0
Repayment of CCFC Notes	(1,000)		0
Borrowings from project financing, notes payable and other	116		226
Repayments of project financing, notes payable and other	(43)		(46)
Financing costs	(27)		(5)
Stock repurchases	(362)		(290)
Proceeds from exercises of stock options	17		3
Other	1		0
Net cash used in financing activities	(113)		(120)
Net decrease in cash and cash equivalents	(569)		(665)
Cash and cash equivalents, beginning of period	1,284		1,252
Cash and cash equivalents, end of period	715		587
Cash paid during the period for:
Interest, net of amounts capitalized	334		352
Income taxes	21		13
Supplemental disclosure of non-cash investing activities:
Change in capital expenditures included in accounts payable	$ 17		$ 3

[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 hedge ineffectiveness and adjustments to reflect changes in credit default risk exposure.