Accumulated Other Comprehensive Income (Loss) - Income (Expense) Effect of Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Affected Line Item on the Statements of Income [Line Items]
Interest Expense	$ (474)	$ (164)	$ (627)	$ (318)
Other Income (Expense) - net	13	10	13	5
Income Tax Expense (Benefit)	(345)	(40)	(404)	(101)
Income (Loss) from Discontinued Operations (net of income taxes)	555	191	(1,488)	541
Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total After-tax	(3,637)	(28)	(3,702)	(73)
Amounts Reclassified From Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) due to Sale of U.K. Utility Business [Member]
Affected Line Item on the Statements of Income [Line Items]
Income Tax Expense (Benefit)	(660)	0	(660)	0
Income (Loss) from Discontinued Operations (net of income taxes)	(3,578)	0	(3,578)	0
Income before income taxes	(4,238)	0	(4,238)	0
Defined Benefit Plans [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(62)	(59)	(124)	(119)
Income Tax Expense (Benefit)	2	11	24	23
Total After-tax	(60)	(48)	(100)	(96)
Defined Benefit Plans [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) due to Sale of U.K. Utility Business [Member]
Affected Line Item on the Statements of Income [Line Items]
Income before income taxes	(3,577)	0	(3,577)	0
Defined Benefit Plans [Member] | Prior Service Costs [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	9	(1)	9	(2)
Defined Benefit Plans [Member] | Net Actuarial Loss [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(71)	(58)	(133)	(117)
Foreign currency translation adjustments [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) due to Sale of U.K. Utility Business [Member]
Affected Line Item on the Statements of Income [Line Items]
Income before income taxes	(646)	0	(646)	0
Unrealized gains (losses) on qualifying derivatives [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	11	24	(28)	27
Income Tax Expense (Benefit)	(10)	(4)	4	(4)
Total After-tax	1	20	(24)	23
Unrealized gains (losses) on qualifying derivatives [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income (Loss) due to Sale of U.K. Utility Business [Member]
Affected Line Item on the Statements of Income [Line Items]
Income before income taxes	(15)	0	(15)	0
Unrealized gains (losses) on qualifying derivatives [Member] | Interest Rate Swaps [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Interest Expense	14	(2)	13	(4)
Income (Loss) from Discontinued Operations (net of income taxes)	(1)	0	(2)	(1)
Unrealized gains (losses) on qualifying derivatives [Member] | Cross Currency Swaps [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Income (Loss) from Discontinued Operations (net of income taxes)	$ (2)	$ 26	$ (39)	$ 32