Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets		$ 546	$ 627
Total Non Current Regulatory Assets		741	887
TOTAL REGULATORY ASSETS		1,287	1,514
Total Current Regulatory Liabilities		538	408
Total Non Current Regulatory Liabilities		1,363	1,209
TOTAL REGULATORY LIABILITIES		1,901	1,617
Efficiency Program Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		36	9
Total Non Current Regulatory Liabilities		24	14
Brazil Tariff Recoveries Energy Purchases Liability
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		211	105
Total Non Current Regulatory Liabilities		7	30
Brazil Tariff Recoveries Transmission Costs Regulatory Fees And Other Liability
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		249	235
Total Non Current Regulatory Liabilities		170	86
Asset Retirement Obligation Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Liabilities		795	759
Brazil Special Obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Liabilities		362	313
Other Regulatory Liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		42	59
Total Non Current Regulatory Liabilities		5	7
Brazil Tariff Recoveries Energy Purchases Asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets	[1]	319	349
Total Non Current Regulatory Assets	[1]	63	132
Brazil Tariff Recoveries Transmission Costs Regulatory Fees And Other Asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets	[1]	139	212
Total Non Current Regulatory Assets	[1]	18	124
El Salvador Tariff Recoveries
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets	[1]	54	43
Pension Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets		316	227
Income Taxes Recoverable From Customers
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets		87	36
Deferred Midwest Independent Service Operator Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets	[1]	114	129
Other Regulatory Assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets		34	23
Total Non Current Regulatory Assets		143	239
Other current regulatory assets that did not earn a rate of return		34	8
Other noncurrent regulatory assets that did not earn a rate of return		$ 138	$ 237

[1] Past expenditures on which the Company does not earn a rate of return.