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Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Manufactured Gas Plant Sites [Member]
$ in Millions
3 Months Ended
Mar. 31, 2019
USD ($)
Commitments and Contingencies [Line Items]  
Minimum range of estimated future costs $ 15
Maximum range of estimated future costs 31
Current and non-current environmental liabilities 19
IPL [Member]  
Commitments and Contingencies [Line Items]  
Minimum range of estimated future costs 12
Maximum range of estimated future costs 26
Current and non-current environmental liabilities $ 16