Retirement Plan and Postretirement Benefits - NPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	$ (13)	$ (17)
Liability, Defined Benefit Plan, Current	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	8	5
Nevada 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	0	0	$ 0
Nevada Power Company [Member] | NV Energy, Inc. [Member] | Other Noncurrent Liabilities [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(1)	(1)
Qualified Plan [Member] | Nevada 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	19	1	36
Qualified Plan [Member] | Nevada Power Company [Member] | NV Energy, Inc. [Member] | Other Noncurrent Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(26)	(23)
Nonqualified Plan [Member] | Nevada 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	1	$ 0
Nonqualified Plan [Member] | Nevada Power Company [Member] | NV Energy, Inc. [Member] | Other Noncurrent Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Noncurrent	(9)	(10)
Nonqualified Plan [Member] | Nevada Power Company [Member] | NV Energy, Inc. [Member] | Other Current Liabilities [Member] | Other Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability, Defined Benefit Plan, Current	$ 1	$ 1