Regulatory Matters - SPPC - Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 7,311	$ 7,506
Regulatory liabilities		211	160
Regulatory liabilities		$ 7,100	$ 7,346
Federal statutory income tax rate		21.00%	21.00%	35.00%
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[1]	26.8240506329114
Regulatory Liabilities	[1]	$ 2,370	$ 2,426
Other
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		Various
Regulatory Liabilities		$ 713	577
Sierra Pacific Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		538	509
Regulatory liabilities		49	18
Regulatory liabilities		$ 489	$ 491
Federal statutory income tax rate		21.00%	21.00%	35.00%
Sierra Pacific Power Company [Member] | Deferred income taxes
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years	[2]	Various
Regulatory Liabilities	[2]	$ 263	$ 270
Sierra Pacific Power Company [Member] | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period	[3]	38 years
Regulatory Liabilities	[3]	$ 217	210
Sierra Pacific Power Company [Member] | Other
Regulatory Liabilities [Line Items]
Regulatory liability amortization period years		Various
Regulatory Liabilities		$ 58	$ 29

[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.

[3] 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.