Receivables (Narrative) (Details) - IPL [Member] $ in Millions	Dec. 31, 2017 USD ($)
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Limit on cash proceeds to be received from third-party	$ 125.0
Receivables Sold [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Available capacity	$ 91.7

The face amount of accounts receivable that will be sold to other entities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Name:	us-gaap_TradeReceivablesHeldForSaleAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant