Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014 segment		Jun. 30, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of strategic business units					6
Number of reportable segments					6
Reconciliation To Income From Continuing Operations Before Taxes
INCOME FROM CONTINUING OPERATIONS BEFORE TAXES AND EQUITY IN EARNINGS OF AFFILIATES	$ 418		$ 407		$ 536		$ 717
Assets
Total Assets	39,433				39,433				40,411
External [Member]
Revenue
Total Revenue	4,311		3,945		8,573		8,095
Adjusted PTC
Adjusted Pretax Contribution	340	[1]	289	[1]	583	[1]	559	[1]
Reconciliation To Income From Continuing Operations Before Taxes
Unrealized derivative gains (losses)	22		53		32		39
Unrealized foreign currency gains (losses)	(7)		(23)		(33)		(49)
Disposition/acquisition gains (losses)	(2)		23		(1)		26
Impairment losses	(99)		0		(265)		(48)
Loss on extinguishment of debt	(13)		(164)		(147)		(207)
Pretax contribution	241		178		169		320
Add: income from continuing operations before taxes, attributable to noncontrolling interests	197		231		412		403
Less: Net equity in earnings of affiliates	20		2		45		6
INCOME FROM CONTINUING OPERATIONS BEFORE TAXES AND EQUITY IN EARNINGS OF AFFILIATES	418		407		536		717
Operating Segments [Member]
Revenue
Total Revenue	4,315		3,947		8,580		8,098
Adjusted PTC
Adjusted Pretax Contribution	340	[1]	289	[1]	583	[1]	559	[1]
Intersegment Eliminations [Member]
Revenue
Total Revenue	(4)		(2)		(7)		(3)
Adjusted PTC
Adjusted Pretax Contribution	0	[1]	0	[1]	0	[1]	0	[1]
US - Generation [Member]
Assets
Total Assets	9,835				9,835				9,952
US - Generation [Member] | External [Member]
Revenue
Total Revenue	893		858		1,894		1,744
Adjusted PTC
Adjusted Pretax Contribution	83	[1]	66	[1]	161	[1]	201	[1]
US - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	893		858		1,894		1,744
Adjusted PTC
Adjusted Pretax Contribution	80	[1]	63	[1]	155	[1]	196	[1]
US - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	0		0		0		0
Adjusted PTC
Adjusted Pretax Contribution	3	[1]	3	[1]	6	[1]	5	[1]
Andes - Generation [Member]
Assets
Total Assets	7,458				7,458				7,356
Andes - Generation [Member] | External [Member]
Revenue
Total Revenue	723		725		1,343		1,415
Adjusted PTC
Adjusted Pretax Contribution	105	[1]	92	[1]	161	[1]	176	[1]
Andes - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	724		725		1,344		1,415
Adjusted PTC
Adjusted Pretax Contribution	104	[1]	88	[1]	157	[1]	169	[1]
Andes - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	(1)		0		(1)		0
Adjusted PTC
Adjusted Pretax Contribution	1	[1]	4	[1]	4	[1]	7	[1]
Brazil - Generation [Member]
Assets
Total Assets	9,144				9,144				8,388
Brazil - Generation [Member] | External [Member]
Revenue
Total Revenue	1,533		1,230		2,978		2,659
Adjusted PTC
Adjusted Pretax Contribution	115	[1]	78	[1]	185	[1]	121	[1]
Brazil - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	1,533		1,230		2,978		2,659
Adjusted PTC
Adjusted Pretax Contribution	115	[1]	78	[1]	184	[1]	120	[1]
Brazil - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	0		0		0		0
Adjusted PTC
Adjusted Pretax Contribution	0	[1]	0	[1]	1	[1]	1	[1]
MCAC - Generation [Member]
Assets
Total Assets	5,060				5,060				5,075
MCAC - Generation [Member] | External [Member]
Revenue
Total Revenue	692		694		1,329		1,363
Adjusted PTC
Adjusted Pretax Contribution	105	[1]	108	[1]	174	[1]	167	[1]
MCAC - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	692		694		1,330		1,363
Adjusted PTC
Adjusted Pretax Contribution	95	[1]	104	[1]	160	[1]	160	[1]
MCAC - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	0		0		(1)		0
Adjusted PTC
Adjusted Pretax Contribution	10	[1]	4	[1]	14	[1]	7	[1]
EMEA - Generation [Member]
Assets
Total Assets	4,240				4,240				4,191
EMEA - Generation [Member] | External [Member]
Revenue
Total Revenue	305		295		696		638
Adjusted PTC
Adjusted Pretax Contribution	76	[1]	74	[1]	194	[1]	173	[1]
EMEA - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	305		295		696		638
Adjusted PTC
Adjusted Pretax Contribution	73	[1]	72	[1]	188	[1]	168	[1]
EMEA - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	0		0		0		0
Adjusted PTC
Adjusted Pretax Contribution	3	[1]	2	[1]	6	[1]	5	[1]
Asia - Generation [Member]
Assets
Total Assets	2,953				2,953				2,810
Asia - Generation [Member] | External [Member]
Revenue
Total Revenue	163		142		331		275
Adjusted PTC
Adjusted Pretax Contribution	23	[1]	40	[1]	32	[1]	72	[1]
Asia - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue	163		142		331		275
Adjusted PTC
Adjusted Pretax Contribution	23	[1]	40	[1]	31	[1]	71	[1]
Asia - Generation [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	0		0		0		0
Adjusted PTC
Adjusted Pretax Contribution	0	[1]	0	[1]	1	[1]	1	[1]
Corporate Other And Other Eliminations [Member]
Assets
Total Assets	743				743				921
Corporate Other And Other Eliminations [Member] | External [Member]
Revenue
Total Revenue	2		1		2		1
Adjusted PTC
Adjusted Pretax Contribution	(167)	[1]	(169)	[1]	(324)	[1]	(351)	[1]
Corporate Other And Other Eliminations [Member] | Operating Segments [Member]
Revenue
Total Revenue	5		3		7		4
Adjusted PTC
Adjusted Pretax Contribution	(150)	[1]	(156)	[1]	(292)	[1]	(325)	[1]
Corporate Other And Other Eliminations [Member] | Intersegment Eliminations [Member]
Revenue
Total Revenue	(3)		(2)		(5)		(3)
Adjusted PTC
Adjusted Pretax Contribution	(17)	[1]	(13)	[1]	(32)	[1]	(26)	[1]
Discontinued Operations [Member]
Assets
Total Assets	$ 0				$ 0				$ 1,718

[1] Adjusted pretax contribution in each segment before intersegment eliminations includes the effect of intercompany transactions with other segments except for interest, charges for certain management fees and the write-off of intercompany balances.