Segments and Geographic Information Segment and Geographic Information (Assets, Depreciation and Amortization and Capital Expenditures ) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total Assets		$ 33,648	$ 34,603	$ 33,648	$ 32,521
Depreciation and Amortization			1,068	1,045	1,003
Capital Expenditures			1,960	2,551	2,396
Interest Income			268	318	310
Interest Expense			1,038	1,050	1,056
Investments in and Advances to Affiliates		966	835	966	1,114
Net Equity in Earnings (Losses) of Affiliates	$ (112)	(175)	(123)	(172)	39
Operating Segments [Member] | US and Utilities SBU
Segment Reporting Information [Line Items]
Total Assets		13,334	14,464	13,334	12,286
Depreciation and Amortization			534	465	449
Capital Expenditures			1,099	1,484	1,373
Interest Income			17	18	10
Interest Expense			371	301	287
Investments in and Advances to Affiliates		465	568	465	538
Net Equity in Earnings (Losses) of Affiliates			(8)	11	35
Operating Segments [Member] | South America
Segment Reporting Information [Line Items]
Total Assets		11,314	11,329	11,314	10,941
Depreciation and Amortization			294	315	300
Capital Expenditures			650	692	662
Interest Income			64	95	92
Interest Expense			237	285	283
Investments in and Advances to Affiliates		77	13	77	213
Net Equity in Earnings (Losses) of Affiliates			(80)	(129)	15
Operating Segments [Member] | MCAC SBU
Segment Reporting Information [Line Items]
Total Assets		4,770	4,847	4,770	4,462
Depreciation and Amortization			164	183	141
Capital Expenditures			183	344	302
Interest Income			14	22	20
Interest Expense			157	142	124
Investments in and Advances to Affiliates		107	168	107	5
Net Equity in Earnings (Losses) of Affiliates			(11)	(13)	(7)
Operating Segments [Member] | EURASIA [Member]
Segment Reporting Information [Line Items]
Total Assets		3,990	3,621	3,990	4,538
Depreciation and Amortization			63	67	99
Capital Expenditures			9	30	51
Interest Income			171	180	186
Interest Expense			113	127	145
Investments in and Advances to Affiliates		215	1	215	293
Net Equity in Earnings (Losses) of Affiliates			4	(9)	14
Corporate, Non-Segment [Member] | Corporate and Other
Segment Reporting Information [Line Items]
Total Assets		240	342	240	294
Depreciation and Amortization			13	15	14
Capital Expenditures			19	1	8
Interest Income			2	3	2
Interest Expense			160	195	217
Investments in and Advances to Affiliates		$ 102	85	102	65
Net Equity in Earnings (Losses) of Affiliates			$ (28)	$ (32)	$ (18)