Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Receivables [Line Items]
Fair value of deferred proceeds	$ 214.6	$ 119.4
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	214.6	119.4
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	138.3	140.1
Unbilled utility revenues	90.5	97.1
Other receivables	0.4	0.1
Receivables sold to third party	229.2	237.3
Less: cash proceeds	5.0	108.0
Deferred proceeds	224.2	129.3
Less: allowance for doubtful accounts	9.6	9.9
Fair value of deferred proceeds	$ 214.6	$ 119.4