Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 2,837	$ 2,693	$ 8,114	$ 7,887
Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	759		2,176
Other non-606 revenue	18		39
Revenues	777		2,215
Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,898		5,336
Other non-606 revenue	162		563
Revenues	2,060		5,899
US and Utilities [Domain]
Disaggregation of Revenue [Line Items]
Revenues	1,230		3,252
US and Utilities [Domain] | Regulated Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	759		2,176
Other non-606 revenue	18		39
Revenues	777		2,215
US and Utilities [Domain] | Non-regulated revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	386		774
Other non-606 revenue	67		263
Revenues	453		1,037
South America [Member]
Disaggregation of Revenue [Line Items]
Revenues	923		2,664
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	922		2,661
Other non-606 revenue	1		3
Revenues	923		2,664
MCAC [Member]
Disaggregation of Revenue [Line Items]
Revenues	462		1,276
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	440		1,211
Other non-606 revenue	22		65
Revenues	462		1,276
Eurasia - Generation [Member]
Disaggregation of Revenue [Line Items]
Revenues	224		935
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	152		701
Other non-606 revenue	72		234
Revenues	224		935
Corporate Other And Other Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenues	(2)		(13)
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	(2)		(11)
Other non-606 revenue	0		(2)
Revenues	$ (2)		$ (13)