Retirement Plan and Postretirement Benefits - SPPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 5	$ 2
Liability, Defined Benefit Plan, Noncurrent	(17)	(87)
Other current liabilities	0	0
Sierra Pacific Power Company [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	4	1	$ 0
Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(20)	(28)
Qualified Plan [Member] | Sierra Pacific Power Company [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	1	27	0
Qualified Plan [Member] | Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(2)	(12)
Nonqualified Plan [Member] | Sierra Pacific Power Company [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	1	0	$ 0
Nonqualified Plan [Member] | Sierra Pacific Power Company [Member] | Other Noncurrent Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(8)	(9)
Nonqualified Plan [Member] | Sierra Pacific Power Company [Member] | Other Current Liabilities [Member] | NV Energy, Inc. [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other current liabilities	$ (1)	$ (1)