Asset Retirement Obligations - SPPC - Asset Retirement Obligation by Type (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligations By Type [Line Items]
Regulatory liabilities		$ 7,475	$ 7,311
Asset Retirement Obligation		1,341	1,272	$ 985
Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		123	44
Cost of removal
Asset Retirement Obligations By Type [Line Items]
Regulatory liabilities	[1]	2,435	2,370
Sierra Pacific Power Company [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory liabilities		497	538
Asset Retirement Obligation		11	10	$ 10
Sierra Pacific Power Company [Member] | Asbestos [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		5	5
Sierra Pacific Power Company [Member] | Evaporative Ponds and Dry Ash Landfills [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		3	2
Sierra Pacific Power Company [Member] | Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		3	3
Sierra Pacific Power Company [Member] | Cost of removal
Asset Retirement Obligations By Type [Line Items]
Regulatory liabilities	[2]	$ 197	$ 217

[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 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.