Subsidiary Debt Subsidiary Debt - NPC - 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
Nevada Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Next Twelve Months	283
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Two	75
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Three	897
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Four	575
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Five	74
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal Thereafter	2,200
Par value	3,322
Total Long-term Debt Maturities and Capital and Financial Leases Future Minimum Payments	4,104
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	37
Executory costs	129
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	653
Long-term Debt	2,788	$ 3,034
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities	3,285
Nevada Power Company [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	210
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	823
Long-term Debt, Maturities, Repayments of Principal in Year Four	500
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Long-term Debt, Maturities, Repayments of Principal after Year Five	1,292
Par value	2,825
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	37
Executory costs	0
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	0
Long-term Debt	2,788
Nevada Power Company [Member] | Capital and Financial Lease Obligations [Member]
Debt Instrument [Line Items]
Capital and Financial Leases, Future Minimum Payments Due, Next Twelve Months	73
Capital and Financial Leases, Future Minimum Payments Due in Two Years	75
Capital and Financial Leases, Future Minimum Payments Due in Three Years	74
Capital and Financial Leases, Future Minimum Payments Due in Four Years	75
Capital and Financial Leases, Future Minimum Payments Due in Five Years	74
Capital and Financial Leases, Future Minimum Payments Due Thereafter	908
Capital and Financial Leases, Future Minimum Payments Due	1,279
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	0
Executory costs	129
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	653
Capital and Financial Lease Obligations	$ 497