Regulatory Matters - SPPC - Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 7,506	$ 7,511
Regulatory liabilities		160	202
Regulatory liabilities		$ 7,346	$ 7,309
Federal statutory income tax rate		21.00%	35.00%	35.00%
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	$ 2,426	$ 2,349
Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		509	500
Regulatory liabilities		18	19
Regulatory liabilities		$ 491	$ 481
Federal statutory income tax rate		21.00%	35.00%	35.00%
Sierra Pacific Power Company [Member] | Deferred Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[2]	28 years
Regulatory Liabilities	[2]	$ 270	$ 264
Regulatory Liabilities, Amortization Period Unknown	[3]	$ 21	0
Sierra Pacific Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[4]	40 years
Regulatory Liabilities	[4]	$ 210	211
Sierra Pacific Power Company [Member] | Deferred Excess Energy Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		1 year
Regulatory Liabilities		$ 0	8
Sierra Pacific Power Company [Member] | Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 29	$ 17
Tax Cuts and Jobs Act of 2017 [Member]
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		21.00%
Tax Cuts and Jobs Act of 2017 [Member] | Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		21.00%

[1] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices. Amounts are deducted from rate base or otherwise accrue a carrying cost.

[2] Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to accelerated tax depreciation and certain property-related basis differences and other various differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse. Amount includes regulatory liabilities with an indeterminate life of $21 million and $- million as of December 31, 2018 and 2017, respectively. See Note 9 for further discussion of 2017 Tax Reform impacts.

[3] (2)Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices.

[4] Amounts represent estimated costs, as accrued through depreciation rates and exclusive of ARO liabilities, of removing regulated property, plant and equipment in accordance with accepted regulatory practices.