Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 2,537	$ 2,613	$ 5,277	$ 5,194
Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	706		1,417
Other non-606 revenue	10		21
Revenues	716		1,438
Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,627		3,438
Other non-606 revenue	194		401
Revenues	1,821		3,839
US and Utilities [Domain]
Disaggregation of Revenue [Line Items]
Revenues	995		2,022
US and Utilities [Domain] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	706		1,417
Other non-606 revenue	10		21
Revenues	716		1,438
US and Utilities [Domain] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	180		388
Other non-606 revenue	99		196
Revenues	279		584
South America [Member]
Disaggregation of Revenue [Line Items]
Revenues	846		1,741
South America [Member] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Other non-606 revenue	0		0
Revenues	0		0
South America [Member] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	845		1,739
Other non-606 revenue	1		2
Revenues	846		1,741
MCAC [Member]
Disaggregation of Revenue [Line Items]
Revenues	406		814
MCAC [Member] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Other non-606 revenue	0		0
Revenues	0		0
MCAC [Member] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	384		771
Other non-606 revenue	22		43
Revenues	406		814
Eurasia - Generation [Member]
Disaggregation of Revenue [Line Items]
Revenues	292		711
Eurasia - Generation [Member] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Other non-606 revenue	0		0
Revenues	0		0
Eurasia - Generation [Member] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	218		549
Other non-606 revenue	74		162
Revenues	292		711
Corporate Other And Other Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenues	(2)		(11)
Corporate Other And Other Eliminations [Member] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Other non-606 revenue	0		0
Revenues	0		0
Corporate Other And Other Eliminations [Member] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		(9)
Other non-606 revenue	(2)		(2)
Revenues	$ (2)		$ (11)