Regulatory Matters Regulatory Matters - SPPC (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Regulatory Assets and Liabilities [Line Items]
Federal statutory income tax rate		21.00%	35.00%	21.00%	35.00%		35.00%
Tax Cuts and Jobs Act of 2017 [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Federal statutory income tax rate				21.00%
Sierra Pacific Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Federal statutory income tax rate		21.00%	35.00%	21.00%	35.00%		35.00%
Sierra Pacific Power Company [Member] | Tax Cuts and Jobs Act of 2017 [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Federal statutory income tax rate				21.00%
Sierra Pacific Power Company [Member] | Public Utilities Commission, Nevada [Member] | Caesars Entertainment Corporation [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Total impact fee				$ 4
Sierra Pacific Power Company [Member] | Public Utilities Commission, Nevada [Member] | Peppermill Resort Spa Casino [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Total impact fee	$ 3
Scenario, Forecast [Member] | Sierra Pacific Power Company [Member] | Public Utilities Commission, Nevada [Member] | Tax Rate Reduction Rider [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount						$ 25