Receivables (Narrative) (Details) (IPL [Member], USD $) In Millions	6 Months Ended	3 Months Ended	6 Months Ended
Jun. 30, 2011 March 2011 Through March 2012 [Member] Maximum [Member]	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2010 Maximum [Member]	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2010 Maximum [Member]	Jun. 30, 2011	Dec. 31, 2010
Cash proceeds to be received from third-party	$ 160.0	$ 140.0	$ 160.0	$ 140.0	$ 160.0
Maximum cash proceeds to be received from third party as of June 30th						130
Receivables sold						$ 187.8	$ 219.6

The cash inflow associated with the proceeds from sale and collection of receivables during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 15

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 16
-Subparagraph a

Name:	us-gaap_ProceedsFromSaleAndCollectionOfReceivables
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration