Acquisitions, Development and Divestitures - Discontinued Operations (Details) £ in Thousands, $ in Millions	3 Months Ended		6 Months Ended			12 Months Ended	18 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2021 GBP (£)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2021 GBP (£)
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) from Discontinued Operations (net of income taxes)	$ 555	$ 191	$ (1,488)		$ 541
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Total Assets	0		0			$ 18,983	$ 0
Total Liabilities	0		0			11,023	0
Discontinued Operations, Held-for-sale | WPD
Discontinued Operation, Income (Loss) from Discontinued Operation Disclosures [Abstract]
Sales proceeds, net of realized foreign currency hedge losses			10,732	£ 7,800,000
Proceeds from Daily Dividend, Divestiture of Business | £								£ 548
Loss on Sale	38	0	(1,609)		0
Carrying value	12,397		12,397				12,397
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Sale of Disposal Group, Net of Tax	3,600		3,600			4,000	3,600
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues	710	476	1,344		1,090
Operating Expenses	214	228	466		449
Other Income (Expense) - net	136	66	202		196
Interest Expense	116	89	209		183
Income before income taxes	516	225	871		654
Gain (Loss) on Sale	38	0	(1,609)		0
Income tax expense	(1)	34	750		113
Income (Loss) from Discontinued Operations (net of income taxes)	555	191	(1,488)		541
Disposal Group, Including Discontinued Operation, Income Tax Expense Attributable to Realization of Book-Tax Outside Basis, Domestic			647
Disposal Group, Including Discontinued Operation, Income Tax Expense Attributable to Realization of Book-Tax Outside Basis, Foreign			166
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Cash and cash equivalents						266
Accounts receivable and unbilled revenues						389
Price risk management assets						146
Property, plant and equipment, net						14,392
Goodwill						2,558
Other intangibles						413
Pension benefit asset						682
Other assets						137
Total Assets						18,983
Short-term debt and long-term debt due within one year						994
Accounts payable						220
Customer deposits						217
Accrued interest						190
Long-term debt						7,938
Total deferred income taxes						1,032
Price risk management liabilities						137
Other deferred credits and liabilities						295
Total Liabilities						11,023
Net assets						7,960
Gain (Loss) on Sale	38	$ 0	(1,609)		$ 0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Sale of Disposal Group, Net of Tax	$ 3,600		3,600			4,000	3,600
Net Proceeds From Divestiture Of Businesses			10,400
Proceeds from Divestiture of Businesses, before Foreign Currency Hedge Losses | £				£ 7,881,000
Disposal Group, Including Discontinued Operation, Loss on Foreign Currency Hedge Against Sale or Disposition							$ 386
Costs to sell			$ 69
Disposal Group, Including Discontinued Operation, Unrealized Gain (Loss) on Derivatives						$ 125