Segments and Geographic Information Segment and Geographic Information (Revenue and Assets by Country) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		$ 14,963	$ 17,146	$ 15,891
Property, plant and equipment, net		22,816	25,151
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	[1]	3,597	3,828	3,630
Property, plant and equipment, net	[1]	8,028	7,713
United States | Discontinued Operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue			2	23
Total Non-U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		11,366	13,318	12,261
Property, plant and equipment, net		14,788	17,438
Brazil
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		4,666	6,009	5,015
Property, plant and equipment, net		3,286	4,725
Chile
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		1,523	1,624	1,569
Property, plant and equipment, net		4,596	4,012
El Salvador
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		736	832	860
Property, plant and equipment, net		318	304
Dominican Republic
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		632	802	832
Property, plant and equipment, net		783	702
Colombia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		557	552	523
Property, plant and equipment, net		446	430
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		396	533	558
Property, plant and equipment, net		191	324
Argentina
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		399	463	545
Property, plant and equipment, net		193	222
Philippines
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		406	451	497
Property, plant and equipment, net		736	752
Mexico
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		383	434	440
Property, plant and equipment, net		716	733
Bulgaria
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		382	410	422
Property, plant and equipment, net		1,259	1,457
Puerto Rico
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		302	348	328
Property, plant and equipment, net		599	551
Panama
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		297	263	250
Property, plant and equipment, net		1,028	1,030
Jordan
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		248	262	142
Property, plant and equipment, net		470	484
Kazahkstan
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		155	161	156
Property, plant and equipment, net		146	206
SRI LANKA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue		45	107	53
Property, plant and equipment, net		0	7
Cameroon
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	[2]	0	0	0
Property, plant and equipment, net	[2]	0	0
Cameroon | Discontinued Operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue			230	473
Ukraine
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	[3]	0	0	0
Property, plant and equipment, net	[3]	0	0
Ukraine | Discontinued Operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue				187
Vietnam
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	[4]	233	0	0
Property, plant and equipment, net	[4]	2	1,491
Other Non-U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	[5]	6	67	71
Property, plant and equipment, net	[5]	$ 19	$ 8
Other Non-U.S. | Discontinued Operations
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue				$ 6

[1] (1)Excludes revenue of $2 million and $23 million for the years ended December 31, 2014 and 2013, respectively, related to Condon and Mid-West Wind, which are reflected as discontinued operations in the accompanying Consolidated Statements of Operations.

[2] (3) Excludes revenue of $230 million and $473 million for the years ended December 31, 2014 and 2013, respectively, related to Sonel, which is reflected as discontinued operations in the accompanying Consolidated Statements of Operations.

[3] (4) Excludes revenue of $187 million for the years ended December 31, 2013 related to Kievoblenergo and Rivnooblenergo, which are reflected as discontinued operations in the accompanying Consolidated Statements of Operations.

[4] (2) Property, plant & equipment as of December 31, 2015 includes the impact of adopting ASU No. 2014-05, Service Concession Arrangements, on a modified retrospective basis as of January 1, 2015. See Note 1—General and Summary of Significant Accounting Policies for more information.

[5] (5) Excludes revenue of $6 million for the years ended December 31, 2013 related to Saurashtra, which is reflected as discontinued operations in the accompanying Consolidated Statements of Operations.