Fair Value Measurements (Narrative) (Details)	9 Months Ended
Sep. 30, 2017
IPL [Member]
Cumulative preferred stock rate	5.10%

The percentage rate used to calculate dividend payments on preferred stock.

No definition available.

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration