Subsidiary Debt Subsidiary Debt - NPC - Annual Payment on Long-Term Debt (Details) - USD ($) $ in Millions	Jan. 01, 2019	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
Nevada Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Next Twelve Months		578
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Two		652
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Three		80
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Four		76
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal in Year Five		52
Long-term Debt and Capital and Financial Lease Obligations, Repayments of Principal Thereafter		2,018
Par value		2,847
Total Long-term Debt Maturities and Capital and Financial Leases Future Minimum Payments		3,456
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost		31
Executory costs		74
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments		535
Long-term Debt		2,353	$ 2,600
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities		2,816
Nevada Power Company [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months		500
Long-term Debt, Maturities, Repayments of Principal in Year Two		575
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		1,309
Par value		2,384
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost		31
Executory costs		0
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments		0
Long-term Debt		2,353
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		78
Capital and Financial Leases, Future Minimum Payments Due in Two Years		77
Capital and Financial Leases, Future Minimum Payments Due in Three Years		80
Capital and Financial Leases, Future Minimum Payments Due in Four Years		76
Capital and Financial Leases, Future Minimum Payments Due in Five Years		52
Capital and Financial Leases, Future Minimum Payments Due Thereafter		709
Capital and Financial Leases, Future Minimum Payments Due		1,072
Debt Instrument, Unamortized Premium, Discount and Debt Issuance Cost		0
Executory costs		74
Capital and Financial Leases, Future Minimum Payments, Interest Included in Payments		535
Capital and Financial Lease Obligations		463
NV Energy [Member]
Debt Instrument [Line Items]
Par value		4,321
NV Energy [Member] | Nevada Power Company [Member]
Debt Instrument [Line Items]
Par value		$ 2,847
NV Energy [Member] | NPC General and Refunding Mortgage Notes, Series CC [Member] | Subsequent Event [Member] | Nevada Power Company [Member]
Debt Instrument [Line Items]
Par value	$ 500
Debt Instrument, Interest Rate, Stated Percentage	3.70%