Property, Plant and Equipment, Net - SPPC (Details) - Sierra Pacific Power Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Public Utility, Property, Plant and Equipment [Line Items]
Plant, net	$ 3,027	$ 2,962
Construction work- in-progress	137	113
Property, plant and equipment, net	$ 3,164	$ 3,075
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.20%	3.10%	3.10%
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	$ 1,130	$ 1,133
Public Utilities, Property, Plant and Equipment, Distribution	1,754	1,669
Public Utilities, Property, Plant and Equipment, Transmission	908	840
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 189	178
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	25 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	20 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	50 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation, Useful Life	60 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	100 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	100 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years
Regulated Operation [Member] | Natural Gas Processing Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution	$ 429	417
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 15	14
Regulated Operation [Member] | Natural Gas Processing Plant [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	35 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years
Regulated Operation [Member] | Natural Gas Processing Plant [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	70 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years
Regulated Operation [Member] | Common Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common	$ 355	338
Plant in service, net	4,780	4,589
Accumulated depreciation and amortization	(1,755)	(1,629)
Plant, net	$ 3,025	2,960
Regulated Operation [Member] | Common Facilities [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common, Useful Life	5 years
Regulated Operation [Member] | Common Facilities [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common, Useful Life	70 years
Nonregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Plant, net	$ 2	$ 2
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years