Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows from Operating Activities
Net Income/(Loss)	$ 132	$ (352)	$ 315
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Distributions and equity in earnings of unconsolidated affiliates	49	84	2
Bargain purchase gain related to GenOn acquisition	0	0	(296)
Depreciation and amortization	1,523	1,256	950
Provision for bad debts	64	67	45
Amortization of nuclear fuel	46	36	39
Amortization of financing costs and debt discount/premiums	12	33	(31)
Adjustment to loss on debt extinguishment	25	(15)	9
Amortization of intangibles and out-of-market contracts	64	49	146
Amortization of unearned equity compensation	42	38	41
(Gain)/loss on disposals and sales of assets, net	(4)	(3)	11
Impairment losses	97	558	0
Changes in derivative instruments	(61)	164	124
Changes in deferred income taxes and liability for uncertain tax benefits	(154)	(67)	(353)
Changes in nuclear decommissioning trust liability	19	15	37
Cash (used)/provided by changes in other working capital, net of acquisition and disposition effects:
Accounts receivable - trade	(2)	(224)	(131)
Inventory	(245)	11	(172)
Prepayments and other current assets	182	(22)	(26)
Accounts payable	(12)	275	(132)
Accrued expenses and other current liabilities	(26)	(114)	231
Other assets and liabilities	(217)	(453)	278
Net Cash Provided by Operating Activities	1,510	1,270	1,149
Cash Flows from Investing Activities
Acquisition of businesses, net of cash acquired	(2,936)	(494)	(81)
Cash acquired in GenOn acquisition	0	0	983
Capital expenditures	(909)	(1,987)	(3,396)
Decrease/(increase) in restricted cash, net	57	(22)	(66)
(Increase)/decrease in restricted cash to support equity requirements for U.S. DOE funded projects	(206)	(26)	164
Increase (Decrease) in Notes Receivables	25	(11)	(24)
Proceeds from renewable energy grants	916	55	62
Purchases of emission allowances, net of proceeds	(16)	5	(1)
Investments in nuclear decommissioning trust fund securities	(619)	(514)	(436)
Proceeds from sales of nuclear decommissioning trust fund securities	600	488	399
Proceeds from sale of assets, net	203	13	137
Investments in unconsolidated affiliates	(103)	0	(25)
Other	85	(35)	22
Net Cash Used by Investing Activities	(2,903)	(2,528)	(2,262)
Cash Flows from Financing Activities
Payment of dividends to preferred and common stockholders	(196)	(154)	(50)
Net receipts/(payments for) from settlement of acquired derivatives that include financing elements	9	267	(68)
Payment for treasury stock	(39)	(25)	0
Sales proceeds and other contributions from noncontrolling interests in subsidiaries	819	531	347
Proceeds from issuance of common stock	21	16	0
Proceeds from issuance of long-term debt	4,563	1,777	3,165
Payment of debt issuance and hedging costs	(67)	(50)	(35)
Payments for short and long-term debt	(3,827)	(935)	(1,260)
Proceeds from (Payments for) Other Financing Activities	(18)	0	0
Net Cash Provided by Financing Activities	1,265	1,427	2,099
Effect of exchange rate changes on cash and cash equivalents	(10)	(2)	(4)
Net (Decrease)/Increase in Cash and Cash Equivalents	(138)	167	982
Cash and Cash Equivalents at Beginning of Period	2,254	2,087	1,105
Cash and Cash Equivalents at End of Period	$ 2,116	$ 2,254	$ 2,087