Receivables (Narrative) (Details) (USD $) In Millions					3 Months Ended	9 Months Ended
Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 RMT [Member]	Dec. 31, 2010 RMT [Member]	Sep. 30, 2011 IPL [Member] Maximum [Member]	Sep. 30, 2010 IPL [Member] Maximum [Member]	Sep. 30, 2011 IPL [Member] Maximum [Member]	Sep. 30, 2010 IPL [Member] Maximum [Member]	Sep. 30, 2011 IPL [Member] Maximum [Member] March 2011 Through March 2012 [Member]	Sep. 30, 2011 IPL [Member]	Dec. 31, 2010 IPL [Member]	Sep. 30, 2011 WPL [Member]	Dec. 31, 2010 WPL [Member]
Cash proceeds to be received from third-party					$ 160.0	$ 155.0	$ 160.0	$ 160.0	$ 160.0
Receivables sold										204.3	219.6
Customer accounts receivable and unbilled revenues	$ 198.5	$ 120.5	$ 107.0	$ 26.0						$ 108.7	$ 174.1	$ 80.3	$ 84.2

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 Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

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