Receivables (Receivables Sold Under The Agreement) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Receivables [Line Items]
Fair value of deferred proceeds	$ 188.0	$ 187.7
IPL [Member]
Receivables [Line Items]
Fair value of deferred proceeds	188.0	187.7
Receivables Sold [Member] | IPL [Member]
Receivables [Line Items]
Customer accounts receivable	131.2	124.7
Unbilled utility revenues	83.0	95.5
Other receivables	0.9	0.9
Receivables sold to third party	215.1	221.1
Less: cash proceeds	16.0	27.0
Deferred proceeds	199.1	194.1
Less: allowance for expected credit losses	11.1	6.4
Fair value of deferred proceeds	$ 188.0	$ 187.7