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Fair Value (Narrative) (Details)
MWh in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2021
USD ($)
MWh
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Entity Information [Line Items]      
Revisions to cash flow and timing estimates $ 0 $ 1,120 $ 1,100
Debt Issuance Costs, Net 25,200 26,000  
Unamortized debt discount 6,400 6,600  
Asset retirement obligations 189,509 195,236  
Regulatory assets, non-current 656,977 392,801  
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]      
Entity Information [Line Items]      
Derivative, Notional Amount, Purchase (Sales), Net 400,000    
Purchase of Derivative Instruments Interest Rate Swap 400,000    
Sale of Derivative Instruments Interest Rate Swap $ 0    
FTR [Member] | Not Designated as Hedging Instrument [Member]      
Entity Information [Line Items]      
Sale of Units Derivative Instruments Financial Transmission Rights | MWh 0    
Petersburg Unit 1 retirement      
Entity Information [Line Items]      
Regulatory assets, non-current $ 60,100 74,500  
Indianapolis Power And Light Company      
Entity Information [Line Items]      
Revisions to cash flow and timing estimates 0 1,120 $ 1,100
Debt Issuance Costs, Net 17,900 17,400  
Unamortized debt discount 5,855 6,006  
Asset retirement obligations 189,509 195,236  
Regulatory assets, non-current $ 656,977 392,801  
Indianapolis Power And Light Company | FTR [Member] | Not Designated as Hedging Instrument [Member]      
Entity Information [Line Items]      
Sale of Units Derivative Instruments Financial Transmission Rights | MWh 0    
Indianapolis Power And Light Company | Petersburg Unit 1 retirement      
Entity Information [Line Items]      
Regulatory assets, non-current $ 60,100 $ 74,545