Asset Retirement Obligations - SPPC - Asset Retirement Obligation by Type (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities		$ 7,311	$ 7,506
Asset Retirement Obligation		1,272	985	$ 954
Other Plant in Service [Member]
Asset Retirement Obligations By Type [Line Items]
Asset Retirement Obligation		44	42
Cost of removal
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities	[1]	2,370	2,426
Sierra Pacific Power Company [Member]
Asset Retirement Obligations By Type [Line Items]
Regulatory Liabilities		538	509
Asset Retirement Obligation		10	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		2	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]	$ 217	$ 210

[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.