Regulatory Matters - NPC - Other (Details)		1 Months Ended		3 Months Ended	12 Months Ended
		Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) MW	Nov. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent				$ 3,157,000,000	$ 3,157,000,000		$ 2,766,000,000
Nevada Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent				$ 746,000,000	$ 746,000,000		800,000,000
Nevada Power Company [Member] | 255 Megawatts of Coal Energy [Member]
Public Utilities, General Disclosures [Line Items]
Coal-Fired Power Plant Capacity | MW					255
Nevada Power Company [Member] | Navajo Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	[1]			11.00%	11.00%
Regulatory Assets, Noncurrent						$ 12
Nevada Power Company [Member] | Public Utilities Commission, Nevada [Member] | General Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities. Filing Supported Rate Increase (Decrease), Amount			$ 96,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 120,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 93,000,000
One-Time Bill Credit				$ 120,000,000
Nevada Power Company [Member] | Public Utilities Commission, Nevada [Member] | Energy Efficiency Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Customer Refund Liability, Current				$ 8,000,000	$ 8,000,000		$ 8,000,000

[1] Includes amounts related to nuclear fuel.