Property Plant and Equipment Property Plant and Equipment (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment		$ 9,691	$ 8,939
Accumulated Depreciation		(2,088)	(2,307)
Property, plant and equipment, net		7,603	6,632
Electric plant
Property, Plant and Equipment [Line Items]
Property, plant and equipment		9,229	8,453
Plant to be Retired [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	[1]	316	0
CWIP
Property, Plant and Equipment [Line Items]
Property, plant and equipment		$ 146	$ 486

[1] Includes expected retirement of Tolk and conversion of Harrington to natural gas.