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Redeemable Stock of Subsidiaries (Narrative) (Details)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Feb. 28, 2015
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2018
USD ($)
series
quarter
$ / shares
Dec. 31, 2017
USD ($)
quarter
$ / shares
Dec. 31, 2016
USD ($)
Mar. 31, 2017
Sep. 30, 2016
USD ($)
Temporary Equity [Line Items]                  
Temporary Equity, Accretion to Redemption Value         $ 4 $ 25      
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners               6.70%  
Temporary equity carrying amount         879 837 $ 782    
Temporary Equity, Other Changes         34 50      
Temporary Equity, Net Income         2 (14)      
Colon [Domain]                  
Temporary Equity [Line Items]                  
Temporary equity carrying amount [1]         201 159      
Temporary Equity, Other Changes         34 50      
IPALCO Enterprises, Inc. [Member]                  
Temporary Equity [Line Items]                  
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners   30.00%   30.00%          
Temporary equity carrying amount         618 618      
Temporary Equity, Stock Issued During Period, Value, New Issues   $ 134              
Temporary Equity, Other Changes $ 24                
IPL Subsidiary                  
Temporary Equity [Line Items]                  
Temporary equity carrying amount         $ 60 60      
Number of preferred stock series | series         5        
Temporary equity annual dividend requirement         $ 3 $ 3      
Number of consecutive quarters without paid dividends to invoke board of directors election rule | quarter         4 4      
IPL Subsidiary | Minimum                  
Temporary Equity [Line Items]                  
Temporary equity, redemption price per share | $ / shares         $ 100 $ 100      
IPL Subsidiary | Maximum                  
Temporary Equity [Line Items]                  
Temporary equity, redemption price per share | $ / shares         $ 118 $ 118      
DPL Subsidiary                  
Temporary Equity [Line Items]                  
Temporary Equity, Accretion to Redemption Value             5    
Retained Earnings [Member]                  
Temporary Equity [Line Items]                  
Temporary Equity, Net Income           $ 0 0    
Retained Earnings [Member] | IPALCO Enterprises, Inc. [Member]                  
Temporary Equity [Line Items]                  
Sale of subsidiary shares to noncontrolling interests       $ 84 $ 0 0 (84)    
Additional Paid-in Capital [Member]                  
Temporary Equity [Line Items]                  
Sale of subsidiary shares to noncontrolling interests         (3) 13 84    
Temporary Equity, Net Income           0 $ 0    
Redeemable Preferred Stock [Member]                  
Temporary Equity [Line Items]                  
Temporary Equity Reclassification         0       $ (4)
Acquire additional shares through 2016 [Member]                  
Temporary Equity [Line Items]                  
Investment Options, acquisition percentage     17.65%            
Acquire additional shares through 2016 [Member] | IPALCO Enterprises, Inc. [Member]                  
Temporary Equity [Line Items]                  
Sale Agreement, Buyer Option To Purchase Ownership Interest, Sales Price     $ 349            
Other Comprehensive Income (Loss) [Member]                  
Temporary Equity [Line Items]                  
Temporary Equity, Other Changes         $ 2 $ (2)      
[1] Characteristics of quotas are similar to common stock.