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Regulatory Matters (Regulatory Matters Narrative - Duke Energy Indiana) (Details) - Indiana rate case 2019 - IURC - Duke Energy Indiana - USD ($)
$ in Millions
Dec. 04, 2019
Sep. 09, 2019
Jul. 02, 2019
Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]        
Requested rate increase (decrease), amount   $ 395 $ 395  
Rate base       $ 10,200
Requested rate increase (decrease), amended amount $ 396 393    
Amount reduced from initial request   $ 2    
Requested rate increase, percentage     15.00%  
Requested rate increase, percentage, net of tax 15.60%   17.00%