Subsidiary Debt Subsidiary Debt - NPC - Capital and Financial Lease Obligations (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Par value		$ 35,376
Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		28,780
Other long-term debt		28,641	$ 27,354
Nevada Power Company [Member]
Debt Instrument [Line Items]
Par value		3,107
Total Long-term Debt and Capital and Financial Lease Obligations		3,075	3,066
Long-term Debt and Capital and Financial Lease Obligations, Current		842	17
Long-term Debt and Capital and Financial Lease Obligations		2,233	3,049
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.500%, Series O due 2018 [Member]
Debt Instrument [Line Items]
Other long-term debt		324	324
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.500%, Series S due 2018 [Member]
Debt Instrument [Line Items]
Other long-term debt		499	498
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 7.125%, Series V due 2019 [Member]
Debt Instrument [Line Items]
Other long-term debt		499	499
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.650%, Series N due 2036 [Member]
Debt Instrument [Line Items]
Other long-term debt		357	357
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.750%, Series R due 2037 [Member]
Debt Instrument [Line Items]
Other long-term debt		346	345
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 5.375%, Series X due 2040 [Member]
Debt Instrument [Line Items]
Other long-term debt		247	247
Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 5.450%, Series Y due 2041 [Member]
Debt Instrument [Line Items]
Other long-term debt		236	236
Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.80%, Series 2017A, due 2032 [Member]
Debt Instrument [Line Items]
Other long-term debt	[1]	40	0
Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017, Due 2036 [Member]
Debt Instrument [Line Items]
Other long-term debt	[1]	39	0
Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017B, due 2039 [Member]
Debt Instrument [Line Items]
Other long-term debt	[1]	13	0
Nevada Power Company [Member] | Subsidiary Debt [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006A due 2032 [Member]
Debt Instrument [Line Items]
Other long-term debt		0	38
Nevada Power Company [Member] | Subsidiary Debt [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Other long-term debt		475	485
NV Energy [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		4,577
Other long-term debt		4,581	$ 4,582
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 6.500%, Series O due 2018 [Member]
Debt Instrument [Line Items]
Par value		324
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 6.500%, Series S due 2018 [Member]
Debt Instrument [Line Items]
Par value		499
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 7.125%, Series V due 2019 [Member]
Debt Instrument [Line Items]
Par value		500
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 6.650%, Series N due 2036 [Member]
Debt Instrument [Line Items]
Par value		367
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 6.750%, Series R due 2037 [Member]
Debt Instrument [Line Items]
Par value		349
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 5.375%, Series X due 2040 [Member]
Debt Instrument [Line Items]
Par value		250
NV Energy [Member] | Nevada Power Company [Member] | Mortgage Securities, 5.450%, Series Y due 2041 [Member]
Debt Instrument [Line Items]
Par value		250
NV Energy [Member] | Nevada Power Company [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.80%, Series 2017A, due 2032 [Member]
Debt Instrument [Line Items]
Par value	[1]	40
NV Energy [Member] | Nevada Power Company [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017, Due 2036 [Member]
Debt Instrument [Line Items]
Par value	[1]	40
NV Energy [Member] | Nevada Power Company [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017B, due 2039 [Member]
Debt Instrument [Line Items]
Par value	[1]	$ 13
Debt Instrument, Interest Rate, Stated Percentage		1.60%	0.00%
NV Energy [Member] | Nevada Power Company [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006A due 2032 [Member]
Debt Instrument [Line Items]
Par value		$ 0
NV Energy [Member] | Nevada Power Company [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Par value		$ 475
NV Energy [Member] | Nevada Power Company [Member] | Minimum [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		2.75%	2.75%
NV Energy [Member] | Nevada Power Company [Member] | Maximum [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		11.60%	11.60%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		$ 3,107
Other long-term debt		$ 3,088	$ 3,066
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.500%, Series O due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%	6.50%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.500%, Series S due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%	6.50%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 7.125%, Series V due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.125%	7.125%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.650%, Series N due 2036 [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 359
Debt Instrument, Interest Rate, Stated Percentage		6.65%	6.65%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 6.750%, Series R due 2037 [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 348
Debt Instrument, Interest Rate, Stated Percentage		6.75%	6.75%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 5.375%, Series X due 2040 [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 248
Debt Instrument, Interest Rate, Stated Percentage		5.375%	5.375%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Mortgage Securities, 5.450%, Series Y due 2041 [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 244
Debt Instrument, Interest Rate, Stated Percentage		5.45%	5.45%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.80%, Series 2017A, due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.80%	0.00%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017, Due 2036 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.60%	0.00%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | NPC Pollution Control Refunding Revenue Bonds, 1.60%, Series 2017B, due 2039 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.60%	0.00%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Minimum [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006A due 2032 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		0.00%	1.89%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Minimum [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006 due 2036 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		0.00%	1.89%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Minimum [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		2.75%	2.75%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Maximum [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006A due 2032 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		0.00%	1.928%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Maximum [Member] | Pollution Control Revenue Bonds, Variable-Rate, Series 2006 due 2036 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		0.00%	1.928%
NV Energy [Member] | Nevada Power Company [Member] | Subsidiary Debt [Member] | Maximum [Member] | Capital lease obligations, 2.75% to 11.60%, due through 2054 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		11.60%	11.60%

[1] (1) Subject to mandatory purchase by Nevada Power in May 2020 at which date the interest rate may be adjusted from time to time.