Regulatory Matters - SPPC - Other (Details) - Sierra Pacific Power Company [Member] $ in Millions	1 Months Ended		12 Months Ended
	Apr. 30, 2018 USD ($)	Mar. 31, 2017 USD ($) number	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Public Utilities Commission, Nevada [Member]
Public Utilities, General Disclosures [Line Items]
Impact Fee Payment Term | number		3
Public Utilities Commission, Nevada [Member] | Caesars Entertainment Corporation [Member]
Public Utilities, General Disclosures [Line Items]
Total impact fee	$ 3	$ 4
Public Utilities Commission, Nevada [Member] | Tax Rate Reduction Rider [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount			$ 25
Public Utilities Commission, Nevada [Member] | Energy Efficiency Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refund Liability, Current			2	$ 1
Federal Energy Regulatory Commission [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refundable Fees, Refund Payments			$ 1