Property, Plant and Equipment, Net - SPPC (Details) - SPPC - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Plant, net	$ 3,034	$ 3,027
Property, plant and equipment, net	3,265	3,164
Common Facilities
Property, Plant and Equipment [Line Items]
Construction work-in-progress	231	137
Property, plant and equipment, net	3,265	3,164
Regulated | Generation
Property, Plant and Equipment [Line Items]
Generation	1,140	1,130
Transmission	914	908
Distribution	1,806	1,754
General and intangible	$ 199	189
Regulated | Generation | Minimum
Property, Plant and Equipment [Line Items]
Useful life, generation	25 years
Useful life, transmission	50 years
Useful life, distribution	20 years
Useful life, other	5 years
Regulated | Generation | Maximum
Property, Plant and Equipment [Line Items]
Useful life, generation	60 years
Useful life, transmission	100 years
Useful life, distribution	100 years
Useful life, other	70 years
Regulated | Natural Gas Processing Plant
Property, Plant and Equipment [Line Items]
Distribution	$ 433	429
General and intangible	$ 15	15
Regulated | Natural Gas Processing Plant | Minimum
Property, Plant and Equipment [Line Items]
Useful life, distribution	35 years
Useful life, other	5 years
Regulated | Natural Gas Processing Plant | Maximum
Property, Plant and Equipment [Line Items]
Useful life, distribution	70 years
Useful life, other	70 years
Regulated | Common Facilities
Property, Plant and Equipment [Line Items]
Common general	$ 361	355
Utility plant in service	4,868	4,780
Accumulated depreciation and amortization	(1,834)	(1,755)
Plant, net	$ 3,034	3,025
Regulated | Common Facilities | Minimum
Property, Plant and Equipment [Line Items]
Useful life, common general	5 years
Regulated | Common Facilities | Maximum
Property, Plant and Equipment [Line Items]
Useful life, common general	70 years
Nonregulated
Property, Plant and Equipment [Line Items]
Plant, net	$ 0	$ 2
Useful life, other	70 years