Employee Benefit Plans - SPPC - Amounts Payable (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 5
Sierra Pacific Power Company [Member] | NV Energy, Inc. [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	4
Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	25	$ 28
Domestic Plan [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	9
Domestic Plan [Member] | Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	13	12
Domestic Plan [Member] | Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Noncurrent	9	9
Domestic Plan [Member] | Sierra Pacific Power Company [Member] | Other Current Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Liability, Defined Benefit Plan, Current	$ 1	$ 1