Property, Plant and Equipment, Net - NPC (Details) - NPC - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Plant, net	$ 6,611	$ 6,559
Construction work-in-progress	202	142
Property, plant and equipment, net	6,813	6,701
Regulated
Property, Plant and Equipment [Line Items]
Generation	3,776	3,690
Transmission	1,483	1,468
Distribution	3,836	3,771
General and intangible	800	791
Utility plant in service	9,895	9,720
Accumulated depreciation and amortization	(3,285)	(3,162)
Plant, net	$ 6,610	6,558
Regulated | Minimum
Property, Plant and Equipment [Line Items]
Useful life, generation	30 years
Useful life, transmission	45 years
Useful life, distribution	20 years
Useful life, other	5 years
Regulated | Maximum
Property, Plant and Equipment [Line Items]
Useful life, generation	55 years
Useful life, transmission	70 years
Useful life, distribution	65 years
Useful life, other	65 years
Nonregulated
Property, Plant and Equipment [Line Items]
Plant, net	$ 1	$ 1
Useful life, other	45 years