Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets		$ 113	$ 156
Total Non Current Regulatory Assets		$ 530	547
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		9 years
Total regulatory assets		$ 643	703
Total Current Regulatory Liabilities		$ 81	86
Remaining Recovery Period of Regulatory Liabilities		1 year
Total Non Current Regulatory Liabilities		$ 1,090	1,146
Total regulatory liabilities		1,171	1,232
Overcollection of Costs [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		80	83
Deferred Income Tax Charge [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Liabilities		209	246
Asset Retirement Obligation Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Liabilities		863	847
Other Regulatory Liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Liabilities		1	3
Total Non Current Regulatory Liabilities		18	53
El Salvador Tariff Recoveries
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets		56	87
Pension Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets	[1]	262	283
Deferred Midwest Independent Service Operator Costs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets		75	88
Environmental Restoration Costs [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Non Current Regulatory Assets		85	89
Other Regulatory Assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total Current Regulatory Assets		57	69
Total Non Current Regulatory Assets		$ 108	$ 87

[1] Past expenditures on which the Company earns a rate of return.