Regulatory Matters Regulatory Matters - SPPC (Details) - Sierra Pacific Power Company [Member] - General Rate Case [Member] - Public Utilities Commission, Nevada [Member] - USD ($) $ in Millions	1 Months Ended
	Apr. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Schedule Of Regulatory Assets and Liabilities [Line Items]
Public Utilities, Interim Rate Increase (Decrease), Amount				$ 5
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 5
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 3	$ 5
Public Utilities, Revenue Sharing, Percent			50.00%
Public Utilities, Approved Return on Equity, Percentage			10.00%
Forecast [Member] | Subsequent Event [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Public Utilities, Interim Rate Increase (Decrease), Amount	$ 3
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 2