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Asset Retirement Obligations Asset Retirement Obligations - NPC - 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, Revision of Estimate 257 10
Retirements (61) (45)
Asset Retirement Obligation, Accretion Expense 48 38
Ending Balance 1,272 985
Asset Retirement Obligation, Current 167 43
Asset Retirement Obligations, Noncurrent 1,105 942
Nevada Power Company [Member]    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning Balance 83 80
Asset Retirement Obligation, Revision of Estimate 6 11
Retirements (19) (11)
Asset Retirement Obligation, Accretion Expense 4 3
Ending Balance 74 83
Asset Retirement Obligation, Current 14 13
Asset Retirement Obligations, Noncurrent $ 60 $ 70