Subsidiary Debt Subsidiary Debt - SPPC - Capital and Financial Lease Obligations (Details) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Par value		$ 37,014
Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		28,263
Other long-term debt		28,097		$ 28,641
NV Energy [Member]
Debt Instrument [Line Items]
Par value		4,321
Other long-term debt		4,318		4,581
NV Energy [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Par value		4,321
Other long-term debt		4,318		4,581
Sierra Pacific Power Company [Member]
Debt Instrument [Line Items]
Par value		1,159
Total Long-term Debt and Capital and Financial Lease Obligations		1,158		1,154
Long-term Debt and Capital and Financial Lease Obligations, Current		3		2
Long-term Debt and Capital and Financial Lease Obligations		1,155		1,152
Long-term Debt and Capital and Financial Lease Obligations, Including Current Maturities		$ 1,158		$ 1,154
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		$ 249		$ 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		$ 396
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
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
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
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
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
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
Sierra Pacific Power Company [Member] | Capital lease obligations, 2.700% to 10.297%, due through 2054 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
Other long-term debt				34
Sierra Pacific Power Company [Member] | NV Energy [Member]
Debt Instrument [Line Items]
Par value		1,159
Other long-term debt		1,159		1,156
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member]
Debt Instrument [Line Items]
Par value		250
Other long-term debt		$ 249		$ 249
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 3.375%, Series T due 2023 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
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
Other long-term debt		$ 396		$ 396
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 2.600%, Series U due 2026 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
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
Other long-term debt		$ 256		$ 256
Sierra Pacific Power Company [Member] | NV Energy [Member] | Mortgage securities, 6.750%, Series P due 2037 [Member] | Subsidiary Debt [Member]
Debt Instrument [Line Items]
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
Other long-term debt		$ 20	[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
Other long-term debt		$ 58	[1]	$ 58
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
Other long-term debt		$ 62	[2]	$ 63
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
Other long-term debt		30		$ 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
Other long-term debt		25		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
Other long-term debt		25		25
Sierra Pacific Power Company [Member] | NV Energy [Member] | Capital lease obligations, 2.700% to 10.297%, due through 2054 [Member]
Debt Instrument [Line Items]
Par value		38
Other long-term debt		$ 38		$ 34

[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.