Retirement Plan and Postretirement Benefits - NPC (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]
Liability, Defined Benefit Plan, Noncurrent	$ 17	$ 87
Liability, Defined Benefit Plan, Current	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	5	2
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	4
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	1	36	0
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	23	24
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		$ 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	10	9
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