Segments (Details) $ in Millions		3 Months Ended
		Mar. 31, 2016 USD ($) segment	Mar. 31, 2015 USD ($)	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 FROM OPERATIONS BEFORE TAXES AND EQUITY IN EARNINGS OF AFFILIATES		$ 160	$ 335
Assets
Total Assets		36,900		$ 36,470
External [Member]
Reconciliation To Income From Continuing Operations Before Taxes
Unrealized derivative gains (losses)		34	15
Unrealized foreign currency gains (losses)		8	(47)
Disposition/acquisition gains		19	5
Impairment losses		(50)	(6)
Loss on extinguishment of debt		(1)	(27)
Pretax contribution		182	192
Add: income from continuing operations before taxes, attributable to noncontrolling interests		(16)	158
Less: Net equity in earnings of affiliates		6	15
Operating Segments [Member]
Revenue
Total Revenue		3,471	3,984
Adjusted PTC
Adjusted Pretax Contribution	[1]	172	252
Intersegment Eliminations [Member]
Revenue
Total Revenue		(6)	(6)
UNITED STATES
Assets
Total Assets		9,890		9,800
UNITED STATES | Operating Segments [Member]
Revenue
Total Revenue		855	997
Adjusted PTC
Adjusted Pretax Contribution	[1]	85	106
Andes - Generation [Member]
Assets
Total Assets		8,484		8,594
Andes - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue		622	612
Adjusted PTC
Adjusted Pretax Contribution	[1]	61	91
BRAZIL
Assets
Total Assets		6,988		6,419
BRAZIL | Operating Segments [Member]
Revenue
Total Revenue		1,040	1,330
Adjusted PTC
Adjusted Pretax Contribution	[1]	(9)	21
MCAC - Generation [Member]
Assets
Total Assets		4,921		4,820
MCAC - Generation [Member] | Operating Segments [Member]
Revenue
Total Revenue		519	598
Adjusted PTC
Adjusted Pretax Contribution	[1]	48	50
Europe [Member]
Assets
Total Assets		3,140		3,101
Europe [Member] | Operating Segments [Member]
Revenue
Total Revenue		246	330
Adjusted PTC
Adjusted Pretax Contribution	[1]	69	85
Asia [Member]
Assets
Total Assets		3,135		3,099
Asia [Member] | Operating Segments [Member]
Revenue
Total Revenue		194	119
Adjusted PTC
Adjusted Pretax Contribution	[1]	22	12
Corporate Other And Other Eliminations [Member]
Assets
Total Assets		342		541
Corporate Other And Other Eliminations [Member] | Operating Segments [Member]
Revenue
Total Revenue		1	4
Adjusted PTC
Adjusted Pretax Contribution	[1]	(104)	$ (113)
Discontinued Operations [Member]
Assets
Total Assets		$ 0		$ 96

[1] Total Assets March 31, 2016 December 31, 2015US SBU $9,890 $9,800Andes SBU 8,484 8,594Brazil SBU 6,988 6,419MCAC SBU 4,921 4,820Europe SBU 3,140 3,101Asia SBU 3,135 3,099Assets of held-for-sale businesses — 96Corporate and Other 342 541Total Assets $36,900 $36,470