Property, Plant and Equipment, Net - SPPC (Details) - Sierra Pacific Power Company [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,962	$ 2,857
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	113	90
Public Utilities, Property, Plant and Equipment, Net	$ 3,075	$ 2,947
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service	3.10%	3.10%	3.00%
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	$ 1,133	$ 1,132
Public Utilities, Property, Plant and Equipment, Distribution	1,669	1,568
Public Utilities, Property, Plant and Equipment, Transmission	840	812
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 178	$ 185
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	25 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	20 years	20 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	50 years	50 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years	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	60 years
Public Utilities, Property, Plant and Equipment, Distribution, Useful Life	100 years	100 years
Public Utilities, Property, Plant and Equipment, Transmission, Useful Life	100 years	100 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years	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	$ 417	$ 403
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 14	$ 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	35 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	5 years	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	70 years
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years	70 years
Regulated Operation [Member] | Common Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common	$ 338	$ 321
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	4,589	4,435
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	(1,629)	(1,583)
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,960	$ 2,852
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	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	70 years
Nonregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2	$ 5
Nonregulated Operation [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years	70 years
Nonregulated Operation [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years	70 years