v2.4.0.6

Common Equity (Schedule of Capital Contributions) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
IPL [Member] |  |  |
Capital contributions from parent | $ 110.0 | $ 54.0 | $ 50.0
WPL [Member] |  |  |
Capital contributions from parent | 90.0 | 25.0 | 75.0
Resources [Member] |  |  |
Capital contributions from parent | 0 | 65.0 | 0
Corporate Services [Member] |  |  |
Capital contributions from parent | $ 30.0 | $ 0 | $ 0

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- Definition The cash inflow from parent as a source of financing that is recorded as additional paid in capital. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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. + Details
Name: | us-gaap_ProceedsFromContributionsFromParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration