Employee Benefit Plans - SPPC - Amounts Payable (Details) - Sierra Pacific Power Company [Member] - Domestic Plan [Member] - NV Energy, Inc. [Member] - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Other Noncurrent Liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	$ 18	$ 19
Other Noncurrent Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	7	7
Other Noncurrent Liabilities [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	13	13
Other Current Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Current	$ 1	$ 1