Held-for-Sale and Dispositions Dispositions (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Apr. 12, 2019	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of business interests, net of cash and restricted cash sold					$ 41	$ 226
Gain (loss) on disposal and sale of businesses interests		$ 90	$ (16)		117	(9)
Gain (Loss) on Disposition of Assets					37	(21)
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Shady Point [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of business interests, net of cash and restricted cash sold						29
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kazakhstan Hydro [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of business interests, net of cash and restricted cash sold				$ 75
Proceeds from Legal Settlements					45
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal					(30)
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Redondo Beach [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring							$ 24
Gain (Loss) on Disposition of Assets					41
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Kilroot and Ballylumford [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from the sale of business interests, net of cash and restricted cash sold						118
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal						(33)
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Uruguaiana
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal					(90)
Guaranty Liabilities		22			22
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax		14	14		43	36
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Itabo Opco [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax		9	9		28	23
Assets Carrying Amount Disclosure Nonrecurring		$ 211			211
Proceeds from the sale of business interests, net of cash and restricted cash sold					$ 101
Disposal Group Not Discontinued Operation Ownership Interest Sold		43.00%			43.00%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | JORDAN
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax		$ 5	5		$ 15	13
Assets Carrying Amount Disclosure Nonrecurring		$ 167			$ 167
Disposal Group Not Discontinued Operation Ownership Interest Sold		36.00%			36.00%
Kilroot and Ballylumford [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring			$ 114			$ 114
Kilroot and Ballylumford [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group Not Discontinued Operation Ownership Interest Sold			100.00%			100.00%
Kilroot and Ballylumford [Member] | Long Lived Assets Held And Used [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets Carrying Amount Disclosure Nonrecurring	[1]							$ 232
Kazakhstan Hydro [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group Not Discontinued Operation Ownership Interest Sold									100.00%

[1] Represents the carrying values at the dates of measurement, before fair value adjustment.