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Receivables (Narrative) (Details) - USD ($) $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2014 | Sep. 30, 2015 | Dec. 31, 2014
Whiting Petroleum Corporation [Member] |  |  |  |
Receivables [Line Items] |  |  |  |
Final payment of certain future tax benefits expected to be realized |  | $ 26.0 |  |
Receivables Sold [Member] | IPL [Member] |  |  |  |
Receivables [Line Items] |  |  |  |
Receivables sold to third party |  |  | $ 201.2 | $ 204.6
Cash proceeds of receivables sold | [1] |  | 1.0 | 22.0
Deferred proceeds |  |  | $ 195.5 | $ 177.2
[1] | Changes in cash proceeds are presented in “Sales of accounts receivable” in operating activities in Alliant Energy’s and IPL’s cash flows statements.

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- Definition The cash inflow associated with the collection of other receivables not otherwise defined in the taxonomy. + References 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 Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
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