Subsidiary Debt Subsidiary Debt - SPPC - Annual Payment on Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 1,148
Long-term Debt, Maturities, Repayments of Principal in Year Two	985
Long-term Debt, Maturities, Repayments of Principal in Year Three	3,520
Long-term Debt, Maturities, Repayments of Principal in Year Four	2,070
Long-term Debt, Maturities, Repayments of Principal in Year Five	1,589
Long-term Debt, Maturities, Repayments of Principal after Year Five	28,821
Par value	38,133
Long-term Debt	37,972	$ 38,649
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	456
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	4
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	3
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal Thereafter	769
Par value	1,203
Total Long-term Debt Maturities and Capital and Financial Leases Future Minimum Payments	1,240
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	(1)
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	(37)
Long-term Debt	1,165	1,164
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities	1,202	$ 1,190
Eligible Property Subject To Lien Of Mortgages	3,700
Sierra Pacific Power Company [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	450
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	0
Long-term Debt, Maturities, Repayments of Principal after Year Five	716
Par value	1,166
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	1,165
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	4
Capital and Financial Leases, Future Minimum Payments Due in Four Years	4
Capital and Financial Leases, Future Minimum Payments Due in Five Years	3
Capital and Financial Leases, Future Minimum Payments Due Thereafter	53
Capital and Financial Leases, Future Minimum Payments Due	74
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	0
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	(37)
Capital and Financial Lease Obligations	$ 37