Receivables (Narrative) (Details) - IPL [Member] - USD ($) $ in Millions	Apr. 30, 2018	Mar. 31, 2018
Receivables Sold [Member]
Receivables [Line Items]
Available capacity		$ 0.0
Outstanding receivables past due		$ 50.7
Subsequent Event [Member] | Minimum [Member]
Receivables [Line Items]
Limit on cash proceeds	$ 90.0
Subsequent Event [Member] | Maximum [Member]
Receivables [Line Items]
Limit on cash proceeds	$ 110.0