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Asset Retirement Obligation (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset Retirement Obligation $ 462 $ 428 $ 415
Asset Retirement Obligation, Liabilities Incurred 42 19  
Asset Retirement Obligation, Liabilities Settled 20 12  
Asset Retirement Obligation, Accretion Expense 22 21  
Asset Retirement Obligation, Revision of Estimate 3 58  
Asset Retirement Obligations, Sale of Plants (13) (71)  
Asset Retirement Obligation, Other 0 (2)  
IPL Subsidiary [Member]      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset Retirement Obligation, Revision of Estimate   75  
DPL Subsidiary      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset Retirement Obligation, Revision of Estimate   $ 87 $ 32
Asset Retirement Obligations, Sale of Plants 13    
Gener Subsidiary [Member]      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset Retirement Obligation, Liabilities Incurred 17    
Hawaii Subsidiary [Member]      
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Asset Retirement Obligation, Liabilities Incurred $ 12