Acquisitions and Dispositions (International Energy Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended						12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)							$ (26)	$ (6)	$ (30)
Income (Loss) From Discontinued Operations, net of tax	$ 20	$ 4	$ (5)	$ (2)	$ (2)	$ (2)	19	(6)	(408)
Asset Impairment Charges							$ 402	282	18
International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) From Discontinued Operations, net of tax									(534)
Asset Impairment Charges									194
Cumulative foreign currency translation losses									620
Income (Loss) from Discontinued Operation, before Income Tax, Attributable to Parent									(445)
Income tax expense on disposal									126
After-tax loss on disposal									640
Previously Remitted Earnings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)								$ (95)
Previously Remitted Earnings [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Foreign Income Tax Expense (Benefit), Continuing Operations									(95)
Discontinued Operations, Disposed of by Sale [Member] | International Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues									988
Fuel used in electric generation and purchased power									227
Cost of natural gas									43
Operation, maintenance and other									341
Depreciation and amortization									62
Property and other taxes									15
Impairment charges									194
(Loss) Gains on Sales of Other Assets and Other, net									(3)
Other income and expenses, net									58
Interest Expense									82
Pretax loss on disposal									514
(Loss) Income before income taxes									(435)
Income tax expense (benefit)									$ 99