Employee Benefit Plans - NPC - Amounts Payable (Details) - Nevada 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	$ (40)	$ (38)
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	(5)	(5)
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