Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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Electric Capacity Of Wind Project

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
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The net cash outflow or inflow for net proceeds and payments derived from carrying life insurance policies for which the entity is the beneficiary.

+ 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

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Investments (Narrative) (Details) $ in Millions	1 Months Ended	9 Months Ended
Investments (Narrative) (Details) $ in Millions	Jul. 31, 2017 USD ($)	Sep. 30, 2017 USD ($) MW	Sep. 30, 2016 USD ($)
Schedule of Investments [Line Items]
Proceeds from liquidation of company-owned life insurance policies			$ 31
Alliant Energy Finance LLC [Member]
Schedule of Investments [Line Items]
Cash equity ownership interest, ownership percentage		50.00%
Electric capacity of wind farm \| MW		225
Increase in Other Investments assets from acquisition		$ 98
IPL [Member]
Schedule of Investments [Line Items]
Proceeds from liquidation of company-owned life insurance policies			$ 19
Term Loan Credit Agreement [Member] \| Alliant Energy Finance LLC [Member]
Schedule of Investments [Line Items]
Proceeds from issuance of debt	$ 95
Variable-rate term loan credit agreement, period	364 days