Property, Plant and Equipment, Net Property, Plant and Equipment, Net - SPPC (Details) - Sierra Pacific Power Company [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,819	$ 2,760
Property, plant and equipment, net	2,938	2,892
Common Facilities [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	119	132
Property, plant and equipment, net	2,938	2,892
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	1,144	1,144
Public Utilities, Property, Plant and Equipment, Distribution	1,518	1,459
Public Utilities, Property, Plant and Equipment, Transmission	817	786
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 191	181
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member] | Minimum [Member]
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]
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]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Distribution	$ 398	390
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 14	14
Regulated Operation [Member] | Natural Gas Processing Plant [Member] | Minimum [Member]
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]
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]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common	$ 305	294
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	4,387	4,268
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	1,573	1,513
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,814	2,755
Regulated Operation [Member] | Common Facilities [Member] | Minimum [Member]
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]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Common, Useful Life	70 years
Unregulated Operation [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 5	$ 5
Unregulated Operation [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years
Unregulated Operation [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life	70 years