Regulatory Matters Regulatory Matters - NPC (Details) $ in Millions	1 Months Ended
	Mar. 31, 2017 USD ($) MW	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	$ 4,513		$ 4,307
Nevada Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory assets	$ 1,146		$ 1,000
Nevada Power Company [Member] | 257 Megawatts of Coal Energy [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Coal-Fired Power Plant Capacity | MW	257
Regulatory assets	$ 151
Nevada Power Company [Member] | Public Utilities Commission, Nevada [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Total impact fee		$ 15