Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Receivables [Line Items]
Fair value of deferred proceeds	$ 237.0	$ 119.4
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	237.0	119.4
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	154.2	140.1
Unbilled utility revenues	92.1	97.1
Other receivables	0.4	0.1
Receivables sold to third party	246.7	237.3
Less: cash proceeds	1.0	108.0
Deferred proceeds	245.7	129.3
Less: allowance for doubtful accounts	8.7	9.9
Fair value of deferred proceeds	$ 237.0	$ 119.4