Subsidiary Debt Subsidiary Debt - NPC - Annual Payment on Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 1,006
Long-term Debt, Maturities, Repayments of Principal in Year Two	3,544
Long-term Debt, Maturities, Repayments of Principal in Year Three	2,099
Long-term Debt, Maturities, Repayments of Principal in Year Four	1,552
Long-term Debt, Maturities, Repayments of Principal in Year Five	823
Long-term Debt, Maturities, Repayments of Principal after Year Five	27,271
Par value	36,295
Long-term Debt	36,116	$ 37,972
Nevada Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Next Twelve Months	75
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Two	897
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Three	576
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Four	75
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Five	79
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal Thereafter	2,123
Par value	3,100
Total Long-term Debt Maturities and Capital and Financial Leases Future Minimum Payments	3,825
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	34
Executory costs	111
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	614
Long-term Debt	2,581	$ 2,788
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities	3,066
Nevada 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	823
Long-term Debt, Maturities, Repayments of Principal in Year Three	500
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	1,292
Par value	2,615
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	34
Executory costs	0
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	0
Long-term Debt	2,581
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	75
Capital and Financial Leases, Future Minimum Payments Due in Two Years	74
Capital and Financial Leases, Future Minimum Payments Due in Three Years	76
Capital and Financial Leases, Future Minimum Payments Due in Four Years	75
Capital and Financial Leases, Future Minimum Payments Due in Five Years	79
Capital and Financial Leases, Future Minimum Payments Due Thereafter	831
Capital and Financial Leases, Future Minimum Payments Due	1,210
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost	0
Executory costs	111
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments	614
Capital and Financial Lease Obligations	$ 485