Regulatory Matters Regulatory Matters - SPPC (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Regulatory Assets and Liabilities [Line Items]
Federal statutory income tax rate		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%		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] | Subsequent Event [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