Employee Benefit Plans - NPC - Amounts Payable (Details) - Nevada Power Company [Member] - UNITED STATES - NV Energy, Inc. [Member] - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Other Assets [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	$ 4	$ 4
Other Current Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Current	(1)	(1)
Other Noncurrent Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(9)	(9)
Qualified Plan | Other Assets [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	$ 9	$ 8