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Segments Of Business (Narrative) (Details)
12 Months Ended
Dec. 31, 2017
segment
Utility Business [Member]  
Segment Reporting Information [Line Items]  
Number of reportable segments (in segments) 3
IPL [Member]  
Segment Reporting Information [Line Items]  
Number of reportable segments (in segments) 3
WPL [Member]  
Segment Reporting Information [Line Items]  
Number of reportable segments (in segments) 3