Employee Benefit Plans - NPC - Amounts Payable (Details) - Nevada Power Company [Member] - UNITED STATES - NV Energy, Inc. [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other Noncurrent Liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	$ 26	$ 26
Other Noncurrent Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	9	9
Other Noncurrent Liabilities [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	1	1
Other Current Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Current	$ 1	$ 1