Segments (Details) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2016 USD ($)		Sep. 30, 2015 USD ($)		Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of strategic business units | segment						6
Number of reportable segments | segment						6
Reconciliation To Income From Continuing Operations Before Taxes
Income (Loss) from Equity Method Investments		$ (11)		$ (81)		$ (25)	$ (96)
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE TAXES AND EQUITY IN EARNINGS OF AFFILIATES		294		160		445	903
Assets
Total Assets		37,108				37,108		$ 36,470
External [Member]
Reconciliation To Income From Continuing Operations Before Taxes
Unrealized derivative gains (losses)		(5)		12		(1)	29
Unrealized foreign currency gains (losses)		(3)		(5)		(12)	(48)
Disposition/acquisition gains		3		23		5	32
Impairment losses		(24)		(139)		(309)	(175)
Loss on extinguishment of debt		(20)		(21)		(26)	(159)
Pretax contribution		223		185		274	516
Add: income from continuing operations before taxes, attributable to noncontrolling interests		82		56		196	483
INCOME (LOSS) FROM CONTINUING OPERATIONS BEFORE TAXES AND EQUITY IN EARNINGS OF AFFILIATES		294		160		445	903
Operating Segments [Member]
Revenue
Total Revenue		3,542		3,522		10,042	10,936
Adjusted PTC
Adjusted Pretax Contribution	[1]	272		315		617	837
Intersegment Eliminations [Member]
Revenue
Total Revenue		(7)		(10)		(18)	(27)
UNITED STATES
Assets
Total Assets		9,822				9,822		9,800
UNITED STATES | Operating Segments [Member]
Revenue
Total Revenue		916		923		2,582	2,751
Adjusted PTC
Adjusted Pretax Contribution		114	[1]	101	[1]	257	263
Andes - Generation [Member]
Assets
Total Assets		8,858				8,858		8,594
Andes - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue		667		652		1,864	1,894
Adjusted PTC
Adjusted Pretax Contribution		134	[1]	150	[1]	279	322
BRAZIL
Assets
Total Assets		5,975				5,975		5,209
BRAZIL | Operating Segments [Member]
Revenue
Total Revenue		1,027		866		2,761	3,083
Adjusted PTC
Adjusted Pretax Contribution		6	[1]	15	[1]	18	97
MCAC - Generation [Member]
Assets
Total Assets		5,120				5,120		4,820
MCAC - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue		547		597		1,596	1,796
Adjusted PTC
Adjusted Pretax Contribution		74	[1]	92	[1]	197	248
Europe [Member]
Assets
Total Assets		2,766				2,766		3,101
Europe [Member] | Operating Segments [Member]
Revenue
Total Revenue		207		292		675	921
Adjusted PTC
Adjusted Pretax Contribution		24	[1]	45	[1]	127	171
Asia [Member]
Assets
Total Assets		3,204				3,204		3,099
Asia [Member] | Operating Segments [Member]
Revenue
Total Revenue		179		195		574	501
Adjusted PTC
Adjusted Pretax Contribution		22	[1]	24	[1]	70	66
Corporate Other And Other Eliminations [Member]
Assets
Total Assets		357				357		541
Corporate Other And Other Eliminations [Member] | Operating Segments [Member]
Revenue
Total Revenue		6		7		8	17
Adjusted PTC
Adjusted Pretax Contribution		(102)	[1]	$ (112)	[1]	(331)	$ (330)
Discontinued Operations [Member]
Assets
Total Assets		$ 1,006				$ 1,006		$ 1,306

[1] Total AssetsSeptember 30, 2016 December 31, 2015US SBU$9,822 $9,800Andes SBU8,858 8,594Brazil SBU5,975 5,209MCAC SBU5,120 4,820Europe SBU2,766 3,101Asia SBU3,204 3,099Assets of discontinued operations and held-for-sale businesses1,006 1,306Corporate and Other357 541Total Assets$37,108 $36,470