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Asset Retirement Obligations - SPPC - Change in Asset Retirement Obligations (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance $ 985 $ 954
Asset Retirement Obligation, Accretion Expense 48 38
Ending Balance 1,272 985
Asset Retirement Obligations, Noncurrent 1,105 942
Sierra Pacific Power Company [Member]    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance 10 10
Asset Retirement Obligation, Accretion Expense 0 0
Ending Balance 10 10
Asset Retirement Obligations, Noncurrent $ 10 $ 10