Goodwill and Other Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		$ 804	$ 753
Accumulated Amortization		(519)	(481)
Net Balance		285	272
Indefinite-Lived Intangible Assets (Excluding Goodwill)		74	68
Indefinite- lived intangible assets, Amortization		0	0
Intangible Assets, Gross		878	821
Intangible Assets, Net		359	340
Land Use Rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-Lived Intangible Assets (Excluding Goodwill)		47	38
Indefinite- lived intangible assets, Amortization		0	0
Water rights
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-Lived Intangible Assets (Excluding Goodwill)		17	17
Indefinite- lived intangible assets, Amortization		0	0
Other
Finite-Lived Intangible Assets, Net [Abstract]
Indefinite-Lived Intangible Assets (Excluding Goodwill)		10	13
Indefinite- lived intangible assets, Amortization		0	0
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		567	521
Accumulated Amortization		(424)	(388)
Net Balance		143	133
Sales concessions
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		63	63
Accumulated Amortization		(22)	(15)
Net Balance		41	48
Contractual payment rights
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance	[1]	56	66
Accumulated Amortization	[1]	(42)	(46)
Net Balance	[1]	14	20
Management rights
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		28	24
Accumulated Amortization		(13)	(10)
Net Balance		15	14
Land Use Rights [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		25	25
Accumulated Amortization		(1)	0
Net Balance		24	25
Contracts
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance		53	29
Accumulated Amortization		(15)	(12)
Net Balance		38	17
All other
Finite-Lived Intangible Assets, Net [Abstract]
Gross Balance	[2]	12	25
Accumulated Amortization	[2]	(2)	(10)
Net Balance	[2]	$ 10	$ 15

[1] (1) Represent legal rights to receive system reliability payments from the regulator.

[2] Includes renewable energy credits, organization costs, project development rights, and other individually insignificant intangible assets.