Subsidiary Debt Subsidiary Debt - SPPC - 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
NV Energy [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		4,577
Other long-term debt		4,581	4,582
Sierra Pacific Power Company [Member]
Debt Instrument [Line Items]
Par value		1,155
Total Long-term Debt and Capital and Financial Lease Obligations		1,154	1,153
Long-term Debt and Capital and Financial Lease Obligations, Current		2	1
Long-term Debt and Capital and Financial Lease Obligations		1,152	1,152
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities		$ 1,154	$ 1,153
Sierra Pacific Power Company [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.375%	3.375%
Sierra Pacific Power Company [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 248	$ 248
Sierra Pacific Power Company [Member] | Mortgage securities, 2.600%, Series U due 2026 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 396	$ 395
Sierra Pacific Power Company [Member] | Mortgage securities, 6.750%, Series P due 2037 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.75%	6.75%
Sierra Pacific Power Company [Member] | Mortgage securities, 6.750%, Series P due 2037 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 255	$ 255
Sierra Pacific Power Company [Member] | Pollution Control Refunding Revenue Bonds, 1.250%, Series 2016A, due 2029 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt	[1]	20	20
Sierra Pacific Power Company [Member] | Gas facilities refunding revenue bonds, 1.500%, series 2016A, due 2031 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt	[1]	58	58
Sierra Pacific Power Company [Member] | Gas and water facilities refunding revenue bonds, 3.000% series 2016B, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt	[2]	63	64
Sierra Pacific Power Company [Member] | Water facilities refunding revenue bonds, series 2016C, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		30	29
Sierra Pacific Power Company [Member] | Water facilities refunding revenue bonds, series 2016D, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		25	25
Sierra Pacific Power Company [Member] | Water facilities refunding revenue bonds, series 2016E, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 25	$ 25
Sierra Pacific Power Company [Member] | Minimum [Member] | Capital and financial lease obligations, 2.700% to 8.548%, due through 2054 [Member]
Debt Instrument [Line Items]
Variable interest rate		2.70%	2.70%
Sierra Pacific Power Company [Member] | Maximum [Member] | Capital and financial lease obligations, 2.700% to 8.548%, due through 2054 [Member]
Debt Instrument [Line Items]
Variable interest rate		10.396%	10.13%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		$ 1,155
Other long-term debt		1,156	$ 1,153
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member]
Debt Instrument [Line Items]
Par value		250
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 249
Debt Instrument, Interest Rate, Stated Percentage		3.375%	3.375%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 2.600%, Series U due 2026 [Member]
Debt Instrument [Line Items]
Par value		$ 400
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 2.600%, Series U due 2026 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 396
Debt Instrument, Interest Rate, Stated Percentage		2.60%	2.60%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 6.750%, Series P due 2037 [Member]
Debt Instrument [Line Items]
Par value		$ 252
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 6.750%, Series P due 2037 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt		$ 256
Debt Instrument, Interest Rate, Stated Percentage		6.75%	6.75%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Pollution Control Refunding Revenue Bonds, 1.250%, Series 2016A, due 2029 [Member]
Debt Instrument [Line Items]
Par value	[1]	$ 20
Sierra Pacific Power Company [Member] | NV Energy [Member] | Pollution Control Refunding Revenue Bonds, 1.250%, Series 2016A, due 2029 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.25%	1.25%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Gas facilities refunding revenue bonds, 1.500%, series 2016A, due 2031 [Member]
Debt Instrument [Line Items]
Par value	[1]	$ 59
Sierra Pacific Power Company [Member] | NV Energy [Member] | Gas facilities refunding revenue bonds, 1.500%, series 2016A, due 2031 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.50%	1.50%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Gas and water facilities refunding revenue bonds, 3.000% series 2016B, due 2036 [Member]
Debt Instrument [Line Items]
Par value	[2]	$ 60
Sierra Pacific Power Company [Member] | NV Energy [Member] | Gas and water facilities refunding revenue bonds, 3.000% series 2016B, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.00%	3.00%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Water facilities refunding revenue bonds, series 2016C, due 2036 [Member]
Debt Instrument [Line Items]
Par value		$ 30
Sierra Pacific Power Company [Member] | NV Energy [Member] | Water facilities refunding revenue bonds, series 2016D, due 2036 [Member]
Debt Instrument [Line Items]
Par value		25
Sierra Pacific Power Company [Member] | NV Energy [Member] | Water facilities refunding revenue bonds, series 2016E, due 2036 [Member]
Debt Instrument [Line Items]
Par value		$ 25
Sierra Pacific Power Company [Member] | NV Energy [Member] | Minimum [Member] | Water facilities refunding revenue bonds, series 2016C, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.69%	0.788%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Minimum [Member] | Water facilities refunding revenue bonds, series 2016D, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.69%	0.788%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Minimum [Member] | Water facilities refunding revenue bonds, series 2016E, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.69%	0.788%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Minimum [Member] | Capital and financial lease obligations, 2.700% to 8.548%, due through 2054 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		2.70%	2.70%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Maximum [Member] | Water facilities refunding revenue bonds, series 2016C, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.84%	0.80%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Maximum [Member] | Water facilities refunding revenue bonds, series 2016D, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.84%	0.80%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Maximum [Member] | Water facilities refunding revenue bonds, series 2016E, due 2036 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		1.84%	0.80%
Sierra Pacific Power Company [Member] | NV Energy [Member] | Maximum [Member] | Capital and financial lease obligations, 2.700% to 8.548%, due through 2054 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Variable interest rate		10.396%	10.13%

[1] (2) Subject to mandatory purchase by Sierra Pacific in June 2019 at which date the interest rate may be adjusted from time to time.

[2] (3) Subject to mandatory purchase by Sierra Pacific in June 2022 at which date the interest rate may be adjusted from time to time.