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Subsidiary Debt Subsidiary Debt - SPPC - Annual Payment on Long-Term Debt (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months $ 2,106  
Long-term Debt, Maturities, Repayments of Principal in Year Two 2,207  
Long-term Debt, Maturities, Repayments of Principal in Year Three 1,342  
Long-term Debt, Maturities, Repayments of Principal in Year Four 1,788  
Long-term Debt, Maturities, Repayments of Principal in Year Five 2,513  
Long-term Debt, Maturities, Repayments of Principal after Year Five 27,058  
Par value 37,014  
Long-term Debt 36,774 $ 35,193
Sierra Pacific Power Company [Member]    
Debt Instrument [Line Items]    
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Next Twelve Months 6  
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Two 4  
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Three 5  
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Four 4  
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Five 254  
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal Thereafter 918  
Par value 1,159  
Total Long-term Debt Maturities and Capital and Financial Leases Future Minimum Payments 1,191  
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost (1)  
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments (32)  
Long-term Debt 1,120 1,120
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities 1,158 $ 1,154
Eligible Property Subject To Lien Of Mortgages 4,100  
Sierra Pacific Power Company [Member] | Long-term Debt [Member]    
Debt Instrument [Line Items]    
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 0  
Long-term Debt, Maturities, Repayments of Principal in Year Two 0  
Long-term Debt, Maturities, Repayments of Principal in Year Three 0  
Long-term Debt, Maturities, Repayments of Principal in Year Four 0  
Long-term Debt, Maturities, Repayments of Principal in Year Five 250  
Long-term Debt, Maturities, Repayments of Principal after Year Five 871  
Par value 1,121  
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost (1)  
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments 0  
Long-term Debt 1,120  
Sierra Pacific Power Company [Member] | Capital and Financial Lease Obligations [Member]    
Debt Instrument [Line Items]    
Capital and Financial Leases, Future Minimum Payments Due, Next Twelve Months 6  
Capital and Financial Leases, Future Minimum Payments Due in Two Years 4  
Capital and Financial Leases, Future Minimum Payments Due in Three Years 5  
Capital and Financial Leases, Future Minimum Payments Due in Four Years 4  
Capital and Financial Leases, Future Minimum Payments Due in Five Years 4  
Capital and Financial Leases, Future Minimum Payments Due Thereafter 47  
Capital and Financial Leases, Future Minimum Payments Due 70  
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost 0  
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments (32)  
Capital and Financial Lease Obligations $ 38