Property, Plant and Equipment, Net Property, Plant and Equipment, Net - SPPC (Details) - Sierra Pacific Power Company [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,911	$ 2,857
Property, plant and equipment, net	2,992	2,947
Common Facilities [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	81	90
Property, plant and equipment, net	2,992	2,947
Regulated Operation [Member] | Electricity Generation Plant, Non-Nuclear [Member]
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Generation or Processing	1,134	1,132
Public Utilities, Property, Plant and Equipment, Distribution	1,631	1,568
Public Utilities, Property, Plant and Equipment, Transmission	828	812
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment	$ 177	185
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	$ 408	403
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	$ 318	321
Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress	4,510	4,435
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation	1,604	1,583
Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress	$ 2,906	2,852
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