Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Revenue
Total Revenue	$ 4,453	$ 4,704	$ 9,487	$ 9,114
Intersegment	(261)	(269)	(555)	(523)
External Revenue	4,192	4,435	8,932	8,591
Reconciliation To Income From Continuing Operations Before Taxes
Depreciation and amortization	341	295	692	576
Interest expense	(385)	(381)	(801)	(719)
Interest income	83	96	174	191
Other expense	(15)	(35)	(44)	(50)
Other income	15	34	33	50
Gain on sale of investments	5	1	184	7
Asset impairment expense	(18)	(33)	(29)	(33)
Foreign currency transaction gains (losses)	(101)	37	(102)	70
Other non-operating expense	(1)	0	(50)	0
Income from continuing operations before taxes and equity in earnings of affiliates	201	614	974	1,309
Assets
Total Assets	42,749		42,749		45,293
Generation Latin America Other [Member]
Revenue
Total Revenue	1,029	1,122	1,988	2,000
Intersegment	(9)	(11)	(19)	(20)
External Revenue	1,020	1,111	1,969	1,980
Adjusted Gross Margin
Adjusted Gross Margin	232	326	519	594
Intersegment	6	3	10	6
External Adjusted Gross Margin	238	329	529	600
Assets
Total Assets	9,120		9,120		9,067
Generation Tiete [Member]
Segment Reporting Information [Line Items]
Generation Capacity (MW)	2,663		2,663
Revenue
Total Revenue	274	256	579	509
Intersegment	(248)	(251)	(530)	(493)
External Revenue	26	5	49	16
Adjusted Gross Margin
Adjusted Gross Margin	210	191	449	393
Intersegment	(248)	(251)	(530)	(493)
External Adjusted Gross Margin	(38)	(60)	(81)	(100)
Assets
Total Assets	1,422		1,422		1,645
Generation North America [Member]
Revenue
Total Revenue	328	339	645	673
Intersegment	0	(4)	0	(4)
External Revenue	328	335	645	669
Adjusted Gross Margin
Adjusted Gross Margin	116	110	222	216
Intersegment	4	(1)	6	3
External Adjusted Gross Margin	120	109	228	219
Assets
Total Assets	3,568		3,568		3,625
Generation Europe [Member]
Revenue
Total Revenue	233	328	683	728
Intersegment	(1)	0	(1)	(1)
External Revenue	232	328	682	727
Adjusted Gross Margin
Adjusted Gross Margin	84	93	321	199
Intersegment	0	1	(7)	2
External Adjusted Gross Margin	84	94	314	201
Assets
Total Assets	3,340		3,340		3,276
Generation Asia [Member]
Revenue
Total Revenue	181	162	362	277
Intersegment	0	0	0	0
External Revenue	181	162	362	277
Adjusted Gross Margin
Adjusted Gross Margin	64	53	122	98
Intersegment	1	0	1	1
External Adjusted Gross Margin	65	53	123	99
Assets
Total Assets	2,099		2,099		1,717
Utilities Latin America [Member]
Revenue
Total Revenue	1,446	1,944	3,180	3,784
Intersegment	0	0	0	0
External Revenue	1,446	1,944	3,180	3,784
Adjusted Gross Margin
Adjusted Gross Margin	44	340	211	660
Intersegment	250	253	535	498
External Adjusted Gross Margin	294	593	746	1,158
Assets
Total Assets	8,491		8,491		9,468
Utilities North America [Member]
Revenue
Total Revenue	678	280	1,410	569
Intersegment	0	0	0	0
External Revenue	678	280	1,410	569
Adjusted Gross Margin
Adjusted Gross Margin	193	89	406	179
Intersegment	1	1	1	1
External Adjusted Gross Margin	194	90	407	180
Assets
Total Assets	9,245		9,245		9,344
Segment Discontinued Operations [Member]
Assets
Total Assets	0		0		1,531
Corporate Other And Other Eliminations [Member]
Revenue
Total Revenue	284	273	640	574
Intersegment	(3)	(3)	(5)	(5)
External Revenue	281	270	635	569
Adjusted Gross Margin
Adjusted Gross Margin	14	(9)	61	34
Intersegment	(12)	(9)	(26)	(22)
External Adjusted Gross Margin	2	(18)	35	12
Assets
Total Assets	$ 5,464		$ 5,464		$ 5,620