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