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Subsidiary Debt Subsidiary Debt - NPC - (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2018
USD ($)
option
Feb. 01, 2019
USD ($)
Dec. 31, 2017
USD ($)
Debt Instrument [Line Items]      
Par value $ 37,014    
Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value 2,847    
Eligible Property Subject To Lien Of Mortgages $ 8,500    
Nevada Power Company [Member] | Building [Member]      
Debt Instrument [Line Items]      
Terms Of Capital Lease 30 years    
Renewal Options Under Capital Lease, Number | option 5    
Number Of Years In Renewal Period 5 years    
Number Of Renewal Options Exercised Under Capital Lease | option 3    
Number Of Additional Renewal Options Under Capital Lease | option 2    
Extended Additional Term Of Capital Lease 10 years    
Capital Leased Assets, Gross $ 23   $ 24
Nevada Power Company [Member] | Land and Building [Member]      
Debt Instrument [Line Items]      
Terms Of Capital Lease 20 years    
Renewal Options Under Capital Lease, Number | option 3    
Number Of Years In Renewal Period 10 years    
Capital Leased Assets, Gross $ 6   0
Nevada Power Company [Member] | Long-Term Energy Purchase Contracts [Member]      
Debt Instrument [Line Items]      
Number Of Years In Renewal Period 30 years    
Capital Leased Assets, Gross $ 30   34
Nevada Power Company [Member] | Equipment [Member]      
Debt Instrument [Line Items]      
Capital Leased Assets, Gross $ 6   3
Nevada Power Company [Member] | ON Line Transmission Line [Member]      
Debt Instrument [Line Items]      
Terms Of Capital Lease 41 years    
Capital Leased Assets, Gross $ 387   396
Utilities Aggregate Share Transmission Line Project 25.00%    
Remaining Share Transmission Line Project 75.00%    
Nevada Power Company [Member] | Nevada Power Company [Member] | ON Line Transmission Line [Member]      
Debt Instrument [Line Items]      
Utilities Aggregate Share Transmission Line Project 95.00%    
Nevada Power Company [Member] | Sierra Pacific Power Company [Member] | ON Line Transmission Line [Member]      
Debt Instrument [Line Items]      
Utilities Aggregate Share Transmission Line Project 5.00%    
NV Energy [Member]      
Debt Instrument [Line Items]      
Par value $ 4,321    
Other long-term debt 4,318   4,581
NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value 2,847    
Other long-term debt $ 2,829   3,088
Minimum [Member] | Nevada Power Company [Member] | Equipment [Member]      
Debt Instrument [Line Items]      
Terms Of Capital Lease 5 years    
Maximum [Member] | Nevada Power Company [Member] | Equipment [Member]      
Debt Instrument [Line Items]      
Terms Of Capital Lease 7 years    
Subsidiary Debt [Member]      
Debt Instrument [Line Items]      
Par value $ 28,263    
Other long-term debt 28,097   28,641
Subsidiary Debt [Member] | NV Energy [Member]      
Debt Instrument [Line Items]      
Par value 4,321    
Other long-term debt 4,318   4,581
NPC Mortgage Securities, 3.70%, Series CC due May 2029 [Member] | Subsequent Event [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value   $ 500  
Debt Instrument, Interest Rate, Stated Percentage   3.70%  
Mortgage Securities, 6.500%, Series O due 2018 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value 0    
Other long-term debt 0   324
Mortgage Securities, 6.500%, Series O due 2018 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt     $ 324
Mortgage Securities, 6.500%, Series O due 2018 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage     6.50%
Mortgage Securities, 6.500%, Series S due 2018 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value 0    
Other long-term debt 0   $ 499
Mortgage Securities, 6.500%, Series S due 2018 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt     $ 499
Mortgage Securities, 6.500%, Series S due 2018 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage     6.50%
Mortgage Securities, 7.125%, Series V due 2019 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value 500    
Other long-term debt $ 500   $ 499
Mortgage Securities, 7.125%, Series V due 2019 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt     $ 499
Mortgage Securities, 7.125%, Series V due 2019 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 7.125%   7.125%
Mortgage Securities, 2.750%, Series BB due 2020 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 575    
Other long-term debt 574   $ 0
Mortgage Securities, 2.750%, Series BB due 2020 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt $ 574   $ 0
Mortgage Securities, 2.750%, Series BB due 2020 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 2.75%   2.75%
Mortgage Securities, 6.650%, Series N due 2036 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 367    
Other long-term debt 360   $ 359
Mortgage Securities, 6.650%, Series N due 2036 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt $ 358   $ 357
Mortgage Securities, 6.650%, Series N due 2036 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.65%   6.65%
Mortgage Securities, 6.750%, Series R due 2037 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 349    
Other long-term debt 348   $ 348
Mortgage Securities, 6.750%, Series R due 2037 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt $ 346   $ 346
Mortgage Securities, 6.750%, Series R due 2037 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 6.75%   6.75%
Mortgage Securities, 5.375%, Series X due 2040 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 250    
Other long-term debt 248   $ 248
Mortgage Securities, 5.375%, Series X due 2040 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt $ 247   $ 247
Mortgage Securities, 5.375%, Series X due 2040 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.375%   5.375%
Mortgage Securities, 5.450%, Series Y due 2041 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 250    
Other long-term debt 244   $ 244
Mortgage Securities, 5.450%, Series Y due 2041 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt $ 236   $ 236
Mortgage Securities, 5.450%, Series Y due 2041 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 5.45%   5.45%
NPC Pollution Control Refunding Revenue Bonds, 1.80%, Series 2017A, due 2032 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value [1] $ 40    
Other long-term debt [1] $ 40   $ 40
NPC Pollution Control Refunding Revenue Bonds, 1.80%, Series 2017A, due 2032 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.80%   1.80%
NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017, Due 2036 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value [1] $ 40    
Other long-term debt [1] $ 39   $ 39
NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017, Due 2036 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.60%   1.60%
NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017B, due 2039 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value [1] $ 13    
Other long-term debt [1] $ 13   $ 13
Debt Instrument, Interest Rate, Stated Percentage 1.60%   1.60%
NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017B, due 2039 [Member] | Subsidiary Debt [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Interest Rate, Stated Percentage 1.60%   1.60%
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Par value $ 463    
Other long-term debt $ 463   $ 475
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | Minimum [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate 2.75%   2.75%
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | Maximum [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate 11.60%   11.60%
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | Subsidiary Debt [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Other long-term debt     $ 475
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | Subsidiary Debt [Member] | Minimum [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate 2.75%   2.75%
Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member] | Subsidiary Debt [Member] | Maximum [Member] | NV Energy [Member] | Nevada Power Company [Member]      
Debt Instrument [Line Items]      
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate 11.60%   11.60%
[1] (1)Subject to mandatory purchase by Nevada Power in May 2020 at which date the interest rate may be adjusted from time to time.