Employee Benefit Plans - SPPC - Amounts Payable (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Domestic Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 73
Sierra Pacific Power Company [Member] | Domestic Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	27	$ 0
Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Domestic Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	4		$ 29
Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	8		9
Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	32		32
Sierra Pacific Power Company [Member] | Other Current Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	$ 1		$ 1