Goodwill and Other Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		$ 1,070	$ 707
Accumulated Amortization		(330)	(307)
Net Balance		740	400
Indefinite-lived Intangible Assets (Excluding Goodwill)		87	69
Indefinite- lived intangible assets, Amortization		0	0
Intangible Assets, Gross		1,157	776
Intangible Assets, Net		827	469
Land Use Rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-lived Intangible Assets (Excluding Goodwill)		39	21
Indefinite- lived intangible assets, Amortization		0	0
Water rights
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-lived Intangible Assets (Excluding Goodwill)		20	20
Indefinite- lived intangible assets, Amortization		0	0
Transmission Rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-lived Intangible Assets (Excluding Goodwill)		22	23
Indefinite- lived intangible assets, Amortization		0	0
Other
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-lived Intangible Assets (Excluding Goodwill)		6	5
Indefinite- lived intangible assets, Amortization		0	0
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		386	367
Accumulated Amortization		(255)	(228)
Net Balance		131	139
Emission allowances [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		64	24
Accumulated Amortization		0	0
Net Balance		64	24
Project Development Rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		203	100
Accumulated Amortization		(5)	(1)
Net Balance		198	99
Contracts
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		157	134
Accumulated Amortization		(38)	(29)
Net Balance		119	105
Other
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		59	43
Accumulated Amortization		(14)	(14)
Net Balance	[1]	45	29
Compensation from Concession Agreement
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		201	39
Accumulated Amortization		(18)	(35)
Net Balance		$ 183	$ 4

[1] Acquired or purchased emissions allowances are finite-lived intangible assets that are expensed when utilized and included in net income for the year. (3)Includes management rights, renewable energy credits and incentives, and other individually insignificant intangible assets.