Regulatory Matters - NPC - Other (Details) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2019 USD ($) MW	Dec. 31, 2019 USD ($) MW	Dec. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Total regulatory assets		$ 2,881	$ 2,881	$ 3,067
Nevada Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Total regulatory assets		$ 801	$ 801	917
Nevada Power Company [Member] | 255 Megawatts of Coal Energy [Member]
Public Utilities, General Disclosures [Line Items]
Coal-Fired Power Plant Capacity | MW		255	255
Nevada Power Company [Member] | Decommissioning costs
Public Utilities, General Disclosures [Line Items]
Total regulatory assets	[1]	$ 241	$ 241	222
Nevada Power Company [Member] | Navajo Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	[2]	11.00%	11.00%
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	$ 8	$ 9
Nevada Power Company [Member] | Public Utilities Commission, Nevada [Member] | Emissions Reduction and Capacity Retirement Plan [Member] | Decommissioning costs
Public Utilities, General Disclosures [Line Items]
Total regulatory assets		$ 12	$ 12

[1] Amount includes regulatory assets with an indeterminate life of $104 million and $81 million as of December 31, 2019 and 2018, respectively.

[2] Includes amounts related to nuclear fuel.