Regulatory Matters - SPPC - Regulatory Liabilities - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		35.00%	35.00%	35.00%
Regulatory Liabilities		$ 7,511	$ 3,120
Regulatory liabilities		202	187
Regulatory liabilities		7,309	2,933
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	$ 2,349	2,242
Regulatory liability amortization period years	[1]	26.845466155811
Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 341	$ 302
Regulatory liability amortization period years		Various
Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Federal statutory income tax rate		35.00%	35.00%	35.00%
Regulatory Liabilities		$ 500	$ 290
Regulatory liabilities		19	69
Regulatory liabilities		$ 481	221
Sierra Pacific Power Company [Member] | Deferred Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		29 years
Regulatory Liabilities		$ 264	6
Sierra Pacific Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		41 years
Regulatory Liabilities		$ 211	205
Sierra Pacific Power Company [Member] | Deferred Excess Energy Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		2 years
Regulatory Liabilities		$ 8	64
Sierra Pacific Power Company [Member] | Regulatory liabilities other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 17	$ 15
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.