Regulatory Matters - SPPC - Other (Details) - Sierra Pacific Power Company [Member] - Public Utilities Commission, Nevada [Member] - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
General Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 5
Public Utilities, Revenue Sharing, Percent		50.00%
Public Utilities, Approved Return on Equity, Percentage		10.00%
General Rate Case [Member] | Forecast [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 3
Energy Efficiency Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refund Liability, Current		$ 2	$ 2